Fixed use of k8s-based postgresql

[k-popov]

Pull Request

Description of the change

The change fixes use of kubernetes-based PostgreSQL installed by postgresql subchart.
Before the patch PostgreSQL instance was created but not used by NextCloud (config was still using SQLite).
The structure of values in NectCloud's chart for postgresql subchart was different from one in postgresql chart itself which caused incorrect user and database creation.

Benefits

Now if postgresql.enabled is set to true with all other values kept default, the instance of PostgreSQL is created in kubernetes cluster and used by NextCloud instance being installed.

Possible drawbacks

Not found.

Applicable issues

#15 or #168 or #226 (probably)

Additional information

None

Checklist

• DCO has been signed off on the commit.
• Chart version bumped in Chart.yaml according to semver.
• (optional) Variables are documented in the README.md

[tvories]

Nice submission!