Add generic OAuth2/OIDC authentication

[palash247]

Discussed in https://github.com/getredash/redash/discussions/6562

^{Originally posted by lucasfcnunes October 30, 2023}

No generic OAuth2 (only Google) nor OIDC mentions

https://redash.io/help/user-guide/users/authentication-options

References

https://openid.net/developers/how-connect-works/

[palash247]

I was able to tweak the Google OIDC authentication flow to work with AWS Cognito and Google simultaneously. Will open a WIP PR soon.