Mainteance: rate-limit some auth entrypoints

[pcrespov]

• replace @global_rate_limit_route by traeffik rate-limit e.g.auth_check_registration_invitation and auth_register. Check with @mrnicegyu11
• ban system on abuse?

[mrnicegyu11]

Just FYI: I am not monitoring github issues, please file all ops-issues in the osparc-ops-environments repo on git.speag.com, thanks. I will unassign myself to avoid confusion for now, if you want discussion input feel free to CC me :)

Thanks a lot!