`use_custom_oauth` discussion

[Krzysztof-Cieslak]

So, use_custom_oauth is left in the core Saturn library, and specific implementations (Google, GitHub) has been moved to Saturn.Extensions.Authentication.

1. Should it still be in Core?
2. Should it be named use_custom_oauth ? maybe something like use_oauth would be better?

[rmunn]

Some thoughts:

• I like the use_oauth name, but maybe it should be called use_oauth_with_config to reflect the pattern of the other, third-party implementations. (Or useOAuthWithConfig, of course).
• All the OAuth implementations have pretty much the same ev.OnCreatingTicket implementation. That seems like it would be useful to factor out into a helper method, so that anyone using the "basic" useOAuthWithConfig wouldn't have to reimplement the wheel.
• Actually, that brings up a thought. There could be a generic useOAuth operation that doesn't require passing a custom config. It would take as parameters not just the clientId/clientSecret/jsonToClaimsMap parameters that the other OAuth implementations take, but also a set of three URLs that define the authorization endpoint, token endpoint, and user information endpoint. Maybe passed in as a record type called OAuthEndpointUrls or something, since all three of them are related and form a natural grouping.
• Refresh tokens are a whole new subject that hasn't even been touched on in the existing implementations.
• I feel like useOAuth should stay in Core, because it's a very commonly-desired feature. Its documentation can then point to the Saturn.Extensions.Authentication package for specific implementations for Google, GitHub, and whatever else gets added. Without an operation like useOAuth in Core, I feel like the other OAuth implementations will be far less likely to be discovered.