feat(ntfy): enable prometheus metrics (#11389)

**Description**
ntfy support prometheus metrics: https://docs.ntfy.sh/config/#monitoring
This PR adds the ckeckbox in questions.yaml and the metrics: section in
values.yaml. The ntfy metrics variable is activated if user selects
prometheus metrics. It is disabled by default

⚒️ Fixes  # <!--(issue)-->

**⚙️ 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

**🧪 How Has This Been Tested?**
<!--
Please describe the tests that you ran to verify your changes. Provide
instructions so we can reproduce. Please also list any relevant details
for your test configuration
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**📃 Notes:**
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**✔️ Checklist:**

- [ ] ⚖️ My code follows the style guidelines of this project
- [x] 👀 I have performed a self-review of my own code
- [ ] #️⃣ I have commented my code, particularly in hard-to-understand
areas
- [ ] 📄 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
- [x] ⬆️ I increased versions for any altered app according to semantic
versioning

**➕ App addition**

If this PR is an app addition please make sure you have done the
following.

- [ ] 🪞 I have opened a PR on
[truecharts/containers](https://github.com/truecharts/containers) adding
the container to TrueCharts mirror repo.
- [ ] 🖼️ I have added an icon in the Chart's root directory called
`icon.png`

---

_Please don't blindly check all the boxes. Read them and only check
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---------

Signed-off-by: polarstack <42521003+polarstack@users.noreply.github.com>

charts/stable/ntfy/Chart.yaml

@@ -18,7 +18,7 @@ name: ntfy
 sources:
   - https://github.com/truecharts/charts/tree/master/charts/stable/ntfy
   - https://github.com/binwiederhier/ntfy/
-version: 6.0.0
+version: 6.0.1
 annotations:
   truecharts.org/catagories: |
     - media

charts/stable/ntfy/questions.yaml

@@ -321,6 +321,8 @@ questions:
                   default: 568
 
 # Include{resources}
+# Include{metrics}
+# Include{prometheusRule}
 # Include{advanced}
 # Include{addons}
 # Include{codeserver}

charts/stable/ntfy/values.yaml

@@ -50,6 +50,7 @@ workload:
             ENABLE_CACHE_FILE: false
             ENABLE_ATTACHMENT_CACHE_DIR: false
             ENABLE_AUTH_FILE: false
+            NTFY_ENABLE_METRICS: "{{ .Values.metrics.main.enabled }}"
             # NTFY_CACHE_DURATION: "12h"
             # NTFY_KEEPALIVE_INTERVAL: "45s"
             # NTFY_MANAGER_INTERVAL: "1m"
@@ -76,3 +77,31 @@ workload:
           envFrom:
             - configMapRef:
                 name: "ntfy"
+
+metrics:
+  main:
+    # -- Enable and configure a Prometheus serviceMonitor for the chart under this key.
+    # @default -- See values.yaml
+    enabled: false
+    type: "servicemonitor"
+    endpoints:
+      - port: main
+        path: /metrics
+    # -- Enable and configure Prometheus Rules for the chart under this key.
+    # @default -- See values.yaml
+    prometheusRule:
+      enabled: false
+      labels: {}
+      # -- Configure additionial rules for the chart under this key.
+      # @default -- See prometheusrules.yaml
+      rules:
+        []
+        # - alert: UnifiPollerAbsent
+        #   annotations:
+        #     description: Unifi Poller has disappeared from Prometheus service discovery.
+        #     summary: Unifi Poller is down.
+        #   expr: |
+        #     absent(up{job=~".*unifi-poller.*"} == 1)
+        #   for: 5m
+        #   labels:
+        #     severity: critical