Helm: support metricRelabelings for loki serviceMonitors (#9784)

**What this PR does / why we need it**:

Add support for `metricRelabelings` in the `ServiceMonitor` resources
when monitoring Loki.

**Checklist**
- [x] Reviewed the
[`CONTRIBUTING.md`](https://github.com/grafana/loki/blob/main/CONTRIBUTING.md)
guide (**required**)
- [x] Documentation added
- [ ] Tests updated
- [x] `CHANGELOG.md` updated
- [ ] If the change is worth mentioning in the release notes, add
`add-to-release-notes` label
- [ ] Changes that require user attention or interaction to upgrade are
documented in `docs/sources/upgrading/_index.md`
- [x] For Helm chart changes bump the Helm chart version in
`production/helm/loki/Chart.yaml` and update
`production/helm/loki/CHANGELOG.md` and
`production/helm/loki/README.md`. [Example
PR](d10549e3ec)

---------

Signed-off-by: Tiago Posse <tiagoposse@gmail.com>
Co-authored-by: Tiago Posse <tiago.posse@hi.health>

docs/sources/installation/helm/reference.md

@@ -2706,6 +2706,15 @@ true
 			<td><pre lang="json">
 {}
 </pre>
+</td>
+		</tr>
+		<tr>
+			<td>monitoring.serviceMonitor.metricRelabelings</td>
+			<td>list</td>
+			<td>ServiceMonitor metric relabel configs to apply to samples before ingestion https://github.com/prometheus-operator/prometheus-operator/blob/main/Documentation/api.md#endpoint</td>
+			<td><pre lang="json">
+[]
+</pre>
 </td>
 		</tr>
 		<tr>

production/helm/loki/CHANGELOG.md

@@ -12,6 +12,10 @@ Entries should be ordered as follows:
 Entries should include a reference to the pull request that introduced the change.
 
 [//]: # (<AUTOMATED_UPDATES_LOCATOR> : do not remove this line. This locator is used by the CI pipeline to automatically create a changelog entry for each new Loki release. Add other chart versions and respective changelog entries bellow this line.)
+## 5.8.6
+
+- [ENHANCEMENT] Add serviceMonitor.metricRelabelings to support metric relabelings
+
 ## 5.8.4
 
 - [ENHANCEMENT] Add loki.lokiCanary.updateStrategy configuration

production/helm/loki/Chart.yaml

@@ -3,7 +3,7 @@ name: loki
 description: Helm chart for Grafana Loki in simple, scalable mode
 type: application
 appVersion: 2.8.2
-version: 5.8.5
+version: 5.8.6
 home: https://grafana.github.io/helm-charts
 sources:
   - https://github.com/grafana/loki

production/helm/loki/README.md

@@ -1,6 +1,6 @@
 # loki
 
-![Version: 5.8.5](https://img.shields.io/badge/Version-5.8.5-informational?style=flat-square) ![Type: application](https://img.shields.io/badge/Type-application-informational?style=flat-square) ![AppVersion: 2.8.2](https://img.shields.io/badge/AppVersion-2.8.2-informational?style=flat-square)
+![Version: 5.8.6](https://img.shields.io/badge/Version-5.8.6-informational?style=flat-square) ![Type: application](https://img.shields.io/badge/Type-application-informational?style=flat-square) ![AppVersion: 2.8.2](https://img.shields.io/badge/AppVersion-2.8.2-informational?style=flat-square)
 
 Helm chart for Grafana Loki in simple, scalable mode
 

production/helm/loki/templates/monitoring/servicemonitor.yaml

@@ -45,6 +45,10 @@ spec:
         {{- with .relabelings }}
         {{- toYaml . | nindent 8 }}
         {{- end }}
+      {{- with .metricRelabelings }}
+      metricRelabelings:
+        {{- toYaml . | nindent 8 }}
+      {{- end }}
       {{- with .scheme }}
       scheme: {{ . }}
       {{- end }}

production/helm/loki/values.yaml

@@ -570,6 +570,9 @@ monitoring:
     # -- ServiceMonitor relabel configs to apply to samples before scraping
     # https://github.com/prometheus-operator/prometheus-operator/blob/master/Documentation/api.md#relabelconfig
     relabelings: []
+    # -- ServiceMonitor metric relabel configs to apply to samples before ingestion
+    # https://github.com/prometheus-operator/prometheus-operator/blob/main/Documentation/api.md#endpoint
+    metricRelabelings: []
     # -- ServiceMonitor will use http by default, but you can pick https as well
     scheme: http
     # -- ServiceMonitor will use these tlsConfig settings to make the health check requests
@@ -1176,8 +1179,8 @@ gateway:
     targetCPUUtilizationPercentage: 60
     # -- Target memory utilisation percentage for the gateway
     targetMemoryUtilizationPercentage:
-  # -- See `kubectl explain deployment.spec.strategy` for more
-  # -- ref: https://kubernetes.io/docs/concepts/workloads/controllers/deployment/#strategy
+    # -- See `kubectl explain deployment.spec.strategy` for more
+    # -- ref: https://kubernetes.io/docs/concepts/workloads/controllers/deployment/#strategy
     # -- Behavior policies while scaling.
     behavior: {}
     #    scaleUp: