draft: Refactor OAuth Social Providers

[UserNobody14]

Refactored the repetitive oauth provider code into a series of handy flexible traits, and added tests for the many different quirks of the providers.

I also believe this is a solution to #215, allowing more configurable scopes to be entered, and eliminating email requirements for providers that may not furnish them for one reason or another.

Looking at ways to reduce the line count on this one, i still feel its a bit repetitive.

[ignatz]

Had a first skim. Looks promising. Never loved the verbosity, so pulling in a second layer for providers that can remain mostly declarative makes a lot of sense 👍

My only concern with the OAuth code in general is that it's hard to impossible to test :/. Did you have the chance to test a one or more providers? 🙏

EDIT: Are you still iterating or is this good to go?

[UserNobody14]

Sorry, wound up caught up in some personal stuff. this is good to go as far as tests and all, but idk, i still feel like its not quite right. Maybe just perfectionism

[ignatz]

FTR: I started upstreaming the most critical changes proposed here. There's a lot going on and I have a hard time wrapping my head around all of them at once (me problem) while ensuring the behavior doesn't change :)

What happened:

• I first tidied up the base trait. The plan was to improve the baseline and in principle allow for golden tests to make sure the behavior doesn't change (though I was to lazy to write tests for all providers).
• Then I pulled out the configurable scopes proposed here. I made it so that OAuthUser can handle optional emails (I see the intent, maybe got lost in the chain?) and policy enforcement.
• Also added the ability for Social OAuth provider to scope down based on UserIdentifier policy.
• Added your Admin UI changes

🙏

IUC, the only thing still missing (probably the lowest priority) is to make "simple" Social providers less verbose by having a shared parametrized implementation. I'll probably also look into this but in due time.

[ignatz]

Update: I simplified many of the providers very much inspired by your proposal incorporating all the other changes (conditional scopes, simplified base trait). It's not quite declarative and I'm sure lines could be saved but it's pretty thin on abstractions and w/ scopes being more conditional, this feels like a reasonable trade-off: https://github.com/trailbaseio/trailbase/blob/dev/crates/core/src/auth/oauth/providers/gitlab.rs

This was some of the most finicky code, thanks for stepping on my toes and this awesome PR 🙏