sourcegraph: add priority class support to redis deployment (#581)

ref: CLO-1017

### Checklist

- [x] Follow the [manual testing
process](https://github.com/sourcegraph/deploy-sourcegraph-helm/blob/main/TEST.md)
- [x] Update
[changelog](https://github.com/sourcegraph/deploy-sourcegraph-helm/blob/main/charts/sourcegraph/CHANGELOG.md)
- [ ] Update [Kubernetes update
doc](https://docs.sourcegraph.com/admin/updates/kubernetes) (no change)

### Test plan

Unit tests.

charts/sourcegraph/CHANGELOG.md

@@ -9,6 +9,7 @@ Use `**BREAKING**:` to denote a breaking change
 ## Unreleased
 
 - Updated OpenTelemetry collector and agent images to run as non-root users [#543](https://github.com/sourcegraph/deploy-sourcegraph-helm/pull/543)
+- redis cache and redis store deployments support priority class
 
 ## 5.6.185
 

charts/sourcegraph/templates/redis/redis-cache.Deployment.yaml

@@ -131,6 +131,9 @@ spec:
         {{- toYaml . | nindent 8 }}
       {{- end }}
       {{- include "sourcegraph.renderServiceAccountName" (list . "redisCache") | trim | nindent 6 }}
+      {{- if .Values.redisCache.priorityClassName }}
+      priorityClassName: {{ .Values.redisCache.priorityClassName }}
+      {{- end }}
       volumes:
       - name: redis-data
         persistentVolumeClaim:

charts/sourcegraph/templates/redis/redis-store.Deployment.yaml

@@ -130,6 +130,9 @@ spec:
         {{- toYaml . | nindent 8 }}
       {{- end }}
       {{- include "sourcegraph.renderServiceAccountName" (list . "redisStore") | trim | nindent 6 }}
+      {{- if .Values.redisStore.priorityClassName }}
+      priorityClassName: {{ .Values.redisStore.priorityClassName }}
+      {{- end }}
       volumes:
       - name: redis-data
         persistentVolumeClaim:

charts/sourcegraph/tests/priorityClass_test.yaml

@@ -104,4 +104,22 @@ tests:
   asserts:
   - equal:
       path: spec.template.spec.priorityClassName
-      value: symbols-class
+      value: symbols-class
+- it: set priority class on redisCache
+  template: redis/redis-cache.Deployment.yaml
+  set:
+    redisCache:
+      priorityClassName: redis-cache-class
+  asserts:
+  - equal:
+      path: spec.template.spec.priorityClassName
+      value: redis-cache-class
+- it: set priority class on redisStore
+  template: redis/redis-store.Deployment.yaml
+  set:
+    redisStore:
+      priorityClassName: redis-store-class
+  asserts:
+  - equal:
+      path: spec.template.spec.priorityClassName
+      value: redis-store-class