Enhancement request - Support other Oauth/OIDC authentication services like Authelia/Keycloak/Authentik

As per title. It would be great if Pastefy would support other open source autentication solutions like those above.

Personally use Authelia as it looks to be the simplest of the 3 I've looked at above. Their Oauth support is currently in beta but is rapidly developing and it works on many services like Gitea, Portainer, Bookstack and Guacacmole.

Thanks for considering.

I'd be very interested in this too. This would allow for protection without having to rely on third parties.

I have a suggestion, instead of choosing between INTERAAPPS, GOOGLE, GITHUB, DISCORD or TWITCH for AUTH_PROVIDER

You should offer environment variables with the following:

AUTH_PROVIDER: CUSTOM
OAUTH2_PROVIDER_AUTHORIZE_URL: 'https://example.com/application/o/authorize/'
OAUTH2_PROVIDER_TOKEN_URL: 'https://example.com/application/o/token/'
OAUTH2_PROVIDER_RESOURCE_URL: 'https://example.com/application/o/userinfo/'
OAUTH2_PROVIDER_REDIRECT_URL: 'https://example.com'
OAUTH2_PROVIDER_LOGOUT_URL: 'https://example.com/application/o/end-session/'
OAUTH2_USER_IDENTIFIER: 'email'
OAUTH2_PROVIDER_SCOPES: 'email openid'