Add SSO support for Google, Facebook, other social media platforms. Also add support for local/no auth.

Requested by rossimc, to allow it to be used at parties, add more SSO providers. Should be possible using Laravel Socialite to use whatever providers someone wants. Possibly even make a generic socialite provider that can be configured and used, then you just need to add the package into composer.json.

Would require a custom build of docker images if we did that, but it's not impossible.