Allow non-SSO deployments

[tlater-famedly]

As of 9995b4c SSO is mandatory, which is obviously not what we want.

The problem is that Zitadel currently sends confirmation emails if no authentication method is enabled on user creation - and since we don't want to pre-set passwords for security reasons, but still don't want to email users for flow reasons, this means we cannot currently provide sync for users that should not use SSO.

Fixing this requires upstream changes to Zitadel, so this is blocked until we have some kind of resolution for zitadel/zitadel#8422

[nikzen]

This is possible now:

POST https://auth.staging.famedly.de/v2/users/human

{
  "userId": "1234567abc",
  "username": "larodar1234567abc",
  "profile": {
    "givenName": "Minnie",
    "familyName": "Mouse",
    "displayName": "Minnie Mouse"
  },
  "email": {
    "email": "[email protected]",
    "isVerified": true
  }
}

Creates a user and no mail is sent. If the user tries to login, zitadel sends a code to set the password