Merge branch 'mattermost-database-bug' into 'master'

Update Default Mattermost Values

Closes #2308

See merge request !5529

chart/templates/mattermost/values.yaml

@@ -164,4 +164,12 @@ mattermostEnvs:
   # required for Keycloak >= 20.X to work with gitlab auth pointed to Keycloak
   MM_GITLABSETTINGS_SCOPE: openid
 
+existingSecretEnvs:
+  # Forces mattermost to use the DB_CONNECTION_STRING in the secret and respect changes in that value
+  - name: MM_SQLSETTINGS_DATASOURCE
+    valueFrom:
+      secretKeyRef:
+        key: DB_CONNECTION_STRING  
+        name: "mattermost-dbcreds"
+
 {{- end -}}