Fix postgres non superuser

[rocketeerbkw]

When dbaas-controller manages a postgres database using a non-superuser, it's not able to provision or delete databases.

Errors provisioning:

postgres db creation failed: postgres db operation create failed: create postgres database error in change owner of database default_9gbWtiPMdjNrIpk0VsSqzodSOGpKV6MIsu26pro1W9LaPiCi1VE4ArQ: pq: must be member of role "9rJDde2oDrZkjZaR" (42501)

Errors deleting:

unable drop database default_9gbWtiPMdjNrIpk0VsSqzodSOGpKV6MIsu26pro1W9LaPiCi1VE4ArQ: pq: must be owner of database default_9gbWtiPMdjNrIpk0VsSqzodSOGpKV6MIsu26pro1W9LaPiCi1VE4ArQ

In order to continue letting provisioned users own the provisioned database, the fix is to grant access to the provisioned user for the dbaas-controller user. That way, it has permission to set owner and delete the database it's not directly an owner of.

Follow up to #34

[rocketeerbkw]

Ran tests at commit refactor: run postgres tests with non-superuser (before the fix). They failed confirming the bug https://github.com/uselagoon/dbaas-controller/actions/runs/24211480340/job/70681118754?pr=56.

[rocketeerbkw]

Tests passing with the fix in place https://github.com/uselagoon/dbaas-controller/actions/runs/24212383544/job/70684296367?pr=56.

[rocketeerbkw]

Added test case for postgres superuser, as suggested in amazeeio/dbaas-operator#74 (review)