chore: Add annotations field to service configuration (#173)

This pull request introduces support for custom Kubernetes service
annotations for the backend service in the RAG infrastructure Helm
chart. The main changes add the ability to specify service annotations
via values, making deployments more flexible and customizable.

**Helm templating improvements:**

* Updated `service.yaml` to conditionally include the `annotations`
field for the backend service if specified in values, using Helm
templating with `toYaml` and `nindent` for proper formatting.

**Configuration enhancements:**

* Added an empty `annotations` map to the `backend.service` section in
`values.yaml`, allowing users to define service annotations for the
backend.

Author: a-klos

infrastructure/rag/templates/backend/service.yaml

@@ -2,6 +2,10 @@ apiVersion: v1
 kind: Service
 metadata:
   name: {{ .Values.backend.name }}
+  {{- with .Values.backend.service.annotations }}
+  annotations:
+    {{- toYaml . | nindent 4 }}
+  {{- end }}
 spec:
   type: {{ .Values.backend.service.type }}
   ports:

infrastructure/rag/values.yaml

@@ -131,6 +131,7 @@ backend:
   service:
     type: ClusterIP
     port: 8080
+    annotations: {}
 
   pythonPathEnv:
     PYTHONPATH: src