Allow to disable user and group management

Allow to disable user and group management: When user and group management is delegated to a third party service (LDAP, OIDC etc.), on might want to disable the user and group management feature in nextcloud. A real life example that happened to me last week: I have a nextcloud installation using nextcloud-oidc-login. This plugins set the groups in a OIDC token, thus user group membership is always reset at login. A user complained to me that users kept leaving the groups he created with the nextcloud interface. I explained him that user and group management should be done in the...