Support service URLs passed via secrets

[HenkvanDyk]

Is your feature request related to a problem? Please describe.
Currently all information related to services such as postgres, elasticsearch, kafka and zookeper are being injected as secrets, including the urls.
This allows adding kafka brokers or moving databases without needing my charts using the services needing to be updated, however the Datahub charts expect theses values to be injected in the template itself.

Describe the solution you'd like
I'd optionally like to set urls by secret reference by allowing a user to pass the secret name and key if it exists, otherwise they can "hardcode" it in the values.yaml.

Describe alternatives you've considered
I could fork the charts, but I'd prefer to keep up to date with changes on datahub charts.

Additional context
Examples of these urls which can be passed as secretKeyRefs:

datahub-helm/charts/datahub/values.yaml

Lines 579 to 582 in 9a8fae1

	bootstrap:
	server: "prerequisites-kafka:9092"
	zookeeper:
	server: "prerequisites-zookeeper:2181"

[github-actions]

This issue is stale because it has been open for 30 days with no activity. If you believe this is still an issue on the latest DataHub release please leave a comment with the version that you tested it with. If this is a question/discussion please head to https://slack.datahubproject.io. For feature requests please use https://feature-requests.datahubproject.io