Implement logging in with external OIDC

[teon]

A lot of users are asking for support with logging in wih external OIDC like Google Workspace/Microsoft Azure ID.
For this we should:

• Add a settings tab: External SSO where we should have a section for configuration of Azure ID (first), Google Workspace (second) + information that configuring external OIDC implies that if the user doesn't exist but will login with external OIDC, then will be created automatically
• If an external OIDC is implemented we need to add "Login with X" on the login page
• If a user logs in with external OIDC and it's not present in our database we create the user
• If the user already exists (login name) then we just log them in
• If the logged in user has configured 2FA we still do it..

[DmitryMigunov]

Will this feature be available on Enterprise only? We are managing users in the Google Workspace. We need synchronization with Google instead of creating users manually in Defguard.