Add paperless-ngx how-to (#10777)

**Description**

Work in progress how-to for paperless-ngx.

**⚙️ Type of change**

- [x] ⚙️ Feature/App addition
- [ ] 🪛 Bugfix
- [ ] ⚠️ Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- [ ] 🔃 Refactor of current code


**📃 Notes:**

This is WIP to gauge if this the right tone for a how-to and to assert
if this would be interesting for TrueCharts.

**✔️ Checklist:**

- [ ] ⚖️ My code follows the style guidelines of this project
- [ ] 👀 I have performed a self-review of my own code
- [ ] #️⃣ I have commented my code, particularly in hard-to-understand
areas
- [x] 📄 I have made corresponding changes to the documentation
- [ ] ⚠️ My changes generate no new warnings
- [ ] 🧪 I have added tests to this description that prove my fix is
effective or that my feature works
- [ ] ⬆️ I increased versions for any altered app according to semantic
versioning

charts/stable/paperless-ngx/docs/how-to.md

@@ -0,0 +1,154 @@
+# Setup Guide
+
+**Paperless-ngx** is an open-source document management system that transforms your physical documents into a searchable
+online archive. Our app is a simple way to install it on your TrueNAS SCALE server.
+
+## Requirements
+
+- Installation of the TrueCharts Catalog, starting [here](/manual/SCALE/guides/getting-started)
+- [`CloundNative-PG`
+  operator](/manual/SCALE/guides/getting-started#cnpg-and-prometheus-operators-installation-and-migration-guide-for-older-users)
+- Paperless-ngx TrueCharts Chart
+
+## Media Storage
+
+- If you plan on importing documents into Paperless-ngx via a network share, for example from a computer or scanner, it
+  is recommended to set up an `NFS Share` for the shared folder. See the [NFS Shares
+  guide](/manual/SCALE/guides/nfs-share) for further information.
+
+## Install Paperless inside TrueNAS SCALE
+
+- Select `Apps` inside the TrueNAS menu.
+- Choose the `Available Applications` tab.
+- Search for `paperless-ngx`.
+
+![Search paperless-ngx](img/search_paperless-ngx.png)
+
+- Click the `Install` button, you'll be prompted to set up Paperless-ngx. You can leave most options at their default
+  values, but:
+  - Check that the `Timezone` is set correctly for this app.
+  - Provide `PAPERLESS_ADMIN_USER`, `PAPERLESS_ADMIN_PASSWORD` and `PAPERLESS_ADMIN_MAIL`, those will only apply on
+    installation, you can change them later in the app.
+  - Enter the URL your Paperless-ngx will be accessible under in `PAPERLESS_URL` if you plan on making your app
+    accessible from the web.
+- If you have set up [Traefik](/charts/enterprise/traefik/how-to/) for ingress click `Enable Ingress` and enter your
+  Paperless-ngx domain in the Hosts section.
+
+![Configure paperless-ngx](img/configure_paperless-ngx.png)
+
+Scroll to the bottom of the window and click `Save`. Once you hit Save Paperless-ngx will be donwloaded and configured. 
+
+Switch back to the `Installed Applications` tab, and wait for the application to switch from `Deploying` to `Active`.
+Once `paperless-ngx` shows `Active` you can click its `Open` button to launch to its login screen. Use the initial Admin
+credentials you provided in the configuration to login.
+
+### Configure additional OCR languages
+
+Paperless-ngx supports different [configuration options](https://docs.paperless-ngx.com/configuration/#ocr) to customize
+how it performs OCR. The most prominent option is the language or languages used to perform OCR operations. You can skip
+this section if you only expect to import documents written in English.
+
+Per default OCR is only performed in English. Check the Paperless-ngx documentation regarding the
+[`PAPERLESS_OCR_LANGUAGE` (singular)](https://docs.paperless-ngx.com/configuration/#ocr) and note what configuration
+would best match your use-case. Paperless-ngx only comes with a few OCR languages pre-installed, see the
+[`PAPERLESS_OCR_LANGUAGES` (plural)](https://docs.paperless-ngx.com/configuration/#docker) configuration option for more
+information, and note if you need this configured too.
+
+Apply those options to your Paperless-ngx installation as follows:
+
+- Select `Apps` inside the TrueNAS menu.
+- You should be on the `Installed Applications` tab.
+- Look for your `paperless-ngx` installation.
+- Click the 3-button menu in its box and select `Edit`. This will open the application configuration pane similar to the
+  configuration page on installation.
+  - Scroll down to the `Extra Environment Variables` section and click `Add`, once or twice depending on whether you
+    need to add one or both of the above options.
+  - Enter each option and its value in a separate box.
+
+![OCR configuration for paperless-ngx](img/ocr_configuration_for_paperless-ngx.png)
+
+Scroll to the bottom of the window and click `Save`. This will reconfigure and restart Paperless-ngx. OCR operations
+performed on documents imported after this change will take the additional languages into account. Those options can be
+changed at any time and will apply to all new OCR operations performed after changes.
+
+### Configure import share
+
+In addition to document uploads via the Web UI, Paperless-ngx can import documents from a [consumption
+directory](https://docs.paperless-ngx.com/usage/#the-consumption-directory). This would allow you to move new documents
+to a shared folder on your TrueNAS SCALE from your computer or directly from your scanner and Paperless-ngx would pick
+up the documents from there. See the explanation of the feature linked above and its [configuration
+options](https://docs.paperless-ngx.com/configuration/#consume_config) for more information.
+
+Due to the [Hast Path Validation Safety](/manual/SCALE/guides/add-storage#host-path-validation-safety) checks of TrueNAS
+SCALE, using storage for an application on your TrueNAS SCALE and with a network share at the same time requires a bit
+of work.  See also the [FAQ](/manual/FAQ#why-i-cant-use-host-path-on-both-my-apps-and-sharing-services) regarding this
+topic.
+
+This guide will only describe the Paperless-ngx specific options required to set up importing documents from a network
+share. Please refer to Part 1 of the [NFS shares with TrueChart apps guide](/manual/SCALE/guides/nfs-share) to prepare
+the NFS share you want to use with Paperless-ngx and note its path. Refer to the [TrueNAS SCALE adding SMB shares
+guide](https://www.truenas.com/docs/scale/scaletutorials/shares/smb/addsmbshares/) to set up network sharing of that
+same folder for Windows computers or scanners offering this functionality.
+
+In addition to adding the NFS share to the Paperless-ngx application we need to configure polling for the import folder.
+The NFS Share and TrueNAS SCALE applications do not support the default polling model Paperless-ngx uses.
+
+Once you have set up the NFS share, configure your Paperless-ngx installation as follows:
+
+- Select `Apps` inside the TrueNAS menu.
+- You should be on the `Installed Applications` tab.
+- Look for your `paperless-ngx` installation.
+- Click the 3-button menu in its box and select `Edit`. This will open the application configuration pane similar to the
+  configuration page on installation.
+  - Scroll down to the `Extra Environment Variables` section and click `Add`.
+  - Enter the name `PAPERLESS_CONSUMER_POLLING` and the value `120`, Paperless-ngx will then look for new documents in
+    the import share every 120 seconds (2 minutes).
+  - Scroll further down to the `To-be consumed Document Storage` section and set `Type of Storage` to `NFS Share`, `NFS
+    Server` to `localhost` and `Path on NFS Server` to the path you configured above.
+
+![Consumer polling configuration for paperless-ngx](img/consumer_polling_configuration_for_paperless-ngx.png)
+![To-be consumed document storage configuration for
+paperless-ngx](img/to-be_consumed_document_storage_configuration_for_paperless-ngx.png)
+
+Scroll to the bottom of the window and click `Save`. This will reconfigure and restart Paperless-ngx. Documents added to
+shared folder will be automatically imported by Paperless-ngx. Those options can be changed at any time, documents still
+in the import share will not be imported anymore though.
+
+### Configure ForwardAuth authentication
+
+Users that have set up [Traefik with ForwardAuth, for example with Authelia](/charts/enterprise/authelia/Setup-Guide/)
+can take advantage of authentication through Authelia for their Paperless-ngx installation. Paperless-ngx will honor
+logins passed from Authelia but not the e-mail address nor the groups of the logged-in user, those will be internal to
+Paperless-ngx and separate from those in Authelia. ForwardAuth can be added to an existing Paperless-ngx installation as
+long as the logins of Authelia users match the logins of Paperless-ngx users.
+
+This guide will only describe the Paperless-ngx specific options required to set up ForwardAuth. Please refer to the
+[Traefik + Authelia ForwardAuth setup guide](/charts/enterprise/authelia/Setup-Guide/) on how to prepare ForwardAuth.
+
+Once you have set up ForwardAuth in your Traefik installation, configure ForwardAuth in Paperless-ngx as follows:
+
+- Select `Apps` inside the TrueNAS menu.
+- You should be on the `Installed Applications` tab.
+- Look for your `paperless-ngx` installation.
+- Click the 3-button menu in its box and select `Edit`. This will open the application configuration pane similar to the
+  configuration page on installation.
+  - Scroll down to the `Extra Environment Variables` section and click `Add` twice.
+  - Enter the name `PAPERLESS_ENABLE_HTTP_REMOTE_USER` and set its value to true, and `PAPERLESS_LOGOUT_REDIRECT_URL`
+    and your logout URL (`https://auth.mydomain.com/logout` as per the above guide's example domain) in the second box.
+
+![ForwardAuth configuration for paperless-ngx](img/forwardauth_configuration_for_paperless-ngx.png)
+
+Scroll to the bottom of the window and click `Save`. This will reconfigure and restart Paperless-ngx. Authentication to
+your Paperless-ngx installation will be handled by Authelia now. Those options can be removed at any time,
+authentication to your Paperless-ngx installation will then revert to the Paperless-ngx built-in authentication
+mechanism.
+
+## Where to go from here?
+
+Paperless-ngx offers a helpful [best practices guide](https://docs.paperless-ngx.com/usage/#basic-searching) as a
+starting point, as well as a recommended workflow a little further along on that same page.
+
+## Support
+
+- You can reach us using [Discord](https://discord.gg/tVsPTHWTtr) for real-time feedback and support.
+- If you found a bug in our chart, open a [GitHub issue](https://github.com/truecharts/apps/issues/new/choose).