feat: configure datastore username and password separately

[MisterTimn]

The chart currently only support setting the datastore URI through values or secret. We deploy postgres using an operator that creates secrets with credentials and want to be able to feed username and password through the secret.

Goals of this PR:

• Add config option for username and password
• Allow config to be fed by a secret
• Move common datastore config to helper function so they can be included (deployment and job both use them)

Working example in our case, using zalando operator to create postgres cluster, the zalando operator creates a secret in the openfga namespace with credentials:

datastore:
  engine: postgres
  uri: postgres://openfga:[email protected]:5432/openfga
  passwordSecret: openfga.openfga.pgobelisk.credentials.postgresql.acid.zalan.do
  usernameSecret: openfga.openfga.pgobelisk.credentials.postgresql.acid.zalan.do

In this PR I have mimicked how the uriSecret functions in that it uses a hard coded reference key (uri, username and password). This is already being used to deploy openfga on our development server.

But I would actually propose to change how uriSecret works similar to bitnami charts, with a configurable secret key:

datastore:
  engine: postgres
  uri: postgres://user:[email protected]:5432/openfga
  externalSecret:
    name: openfga.openfga.pgobelisk.credentials.postgresql.acid.zalan.do
    uriSecretKey: ""
    passwordSecretKey: "password"
    usernameSecretKey: "username"

This would be setup like so:

1. if secretKey for config value is set (default they are null or empty string), then we use the secret
2. secretKey not set, then we use the default

This way you can mix and match values from config and from secrets by setting the reference keys.

Description

References

Review Checklist

• I have clicked on "allow edits by maintainers".
• I have added documentation for new/changed functionality in this PR or in a PR to openfga.dev [Provide a link to any relevant PRs in the references section above]
• The correct base branch is being used, if not main
• I have added tests to validate that the change in functionality is working as expected

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[linux-foundation-easycla]

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• ✅ login: MisterTimn / name: Jasper Vaneessen (4d00e7f, 03533d5, d683b6e, e88f256, 06ab1a8, 0ac6aad)

[MisterTimn]

closing this PR in favor of #140