Add tests for postgres scenarios where external secret is involude

[tumido]

I get scared when I see postgres auth secret values getting changed 😆, mainly because of past stress of trying to satisfy all of the scenarios that tend to cause regression to other values if not done right. Do we have good tests to ensure that when certain values are set, the correct Deployment yaml is generated? As theres a few conditional branches in that backstage.postgresql.databaseSecretKey function. If not, would be good to get these in another time if possible. Will allow us to change any code in this area with increased confidence in future.

I will add though, changes lgtm 👍

Originally posted by @ChrisJBurns in #154 (comment)

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[ChrisJBurns]

Remove stale