Add support for ZITADEL OIDC

[bitfactory-sem-denbroeder]

Describe the feature or potential improvement

Zitadel is an open-source SSO implementation, it works nativly with auth,js and seems to be a rather small integration.

Additional information

No response

[marcklingen]

Hi @bitfactory-sem-denbroeder, open for PRs on this one. You can check how Okta/Auth0 are added throughout the repo.