[Enhancement] Add OAuth/OpenID support

[M-Davies]

Use case

I would like OAuth/OpenID authentication and onboarding support for wger.

Proposal

Simiarly to #812 , I would like more opportunties to hook my existing homelab up to wger.

The immediate benefits I can see are:

• Federated management of users and admins
• Enforcement of multi-factor authentication (MFA) for all users via the OAuth service (e.g. Authentik, Authelia, etc)
• Tracking of user authentication attempts to lock down compromised accounts quicker

Additional Context

Unfortunately, I personally don't have the time or knowledge to implement this massive feature but if anyone would like to take the lead on this, I'd be happy to help out where possible

[rolandgeider]

Hi! you're not the first to ask for this 😅 , e.g. #1797

While it's not full openid support, we're currently working on adding auth header authentication in #1847. Depending on what you might have in mind, it's perhaps enough?

(closing here since there's already an openid ticket)