feat: allow for Postgres password secret generation (#147)

## Description

This allows for the Postgres password secret to be generated in the
config chart directly

## Related Issue

Fixes #145 

## Type of change

- [ ] Bug fix (non-breaking change which fixes an issue)
- [X] New feature (non-breaking change which adds functionality)
- [ ] Other (security config, docs update, etc)

## Checklist before merging

- [X] Test, docs, adr added or updated as needed
- [X] [Contributor Guide
Steps](https://github.com/defenseunicorns/uds-package-gitlab/blob/main/CONTRIBUTING.md#developer-workflow)
followed

chart/templates/postgres-secret.yaml

@@ -0,0 +1,10 @@
+{{- if ne .Values.postgres.password "" }}
+apiVersion: v1
+kind: Secret
+metadata:
+  name: gitlab-postgres
+  namespace: {{ .Release.Namespace }}
+type: kubernetes.io/opaque
+stringData:
+  password: {{ .Values.postgres.password }}
+{{- end }}

chart/values.yaml

@@ -19,6 +19,8 @@ redis:
   namespace: dev-redis
   port: 6379
 postgres:
+  password: ""
+
   # Set to false to use external postgres
   internal: true
   selector: