Allow self hosted instances to restrict registrations to requiring an invite code or just disabling it completely

(#1035) Feature Shipped self-hosting

Thread

Comment by @SolunaCG
RexSystem 1 vote originally by @SolunaCG on GitHub
This would be especially useful if invite-based registrations could be configured with:
  • maximum number of uses
  • expiration dates
  • optional role assignment
  • optional email requirement
Example: A self-hosted operator wants to invite 5 friends to try Fluxer. Instead of opening registrations globally, they create an invite that is valid for 5 registrations and expires after 24 hours. This keeps registrations controlled while making onboarding much easier for small communities.