fix(charts/linkwarden): sso auth issuer never resolving

[helionmusic]

What this PR does / why we need it

Currently in the Linkwarden chart, when attempting to set an issuer url value for a given provider, the template attempts to validate the the issuer value exists in the list of supported auth providers. Instead it should check for provider against that list.

What ends up happening is since the issuer should be a URL, it will never resolve against that list, and thus the *_ISSUER key never gets set.

Checklist

• Chart Version bumped
• User name added to AUTHORS file
• Title of the PR starts with a valid commit scope as detailed in the CONTRIBUTING (e.g.
  fix(charts/linkwarden): ...)

[github-actions]

This PR 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.

[bkoerbel]

This exact issue has blocked me from using this Linkwarden chart with Authentik. Please merge this fix :)

[github-actions]

This PR 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.