Upfront Identity Fetching

[mullermp]

Rework of identity and credentials to be more like SDK v3.

Major changes:

• Simplify identity classes by removing Identity base
• Make all identity providers refreshable by default
• Add expiration and set? into the identity provider interface
• Resolve credentials up front on client config

[richardwang1124]

Why is the options parameter added back into the method header?

[mullermp]

I suppose this is not necessary right now, but I may want to add back the before refresh callback. Is there a use case maybe with token file reading in SSO?

[richardwang1124]

I do see that in v3 we have the before_refresh option in certain providers and @before_refresh member in the RefreshingCredentials, but I don't immediately see where this is used in the SDK code. Going through the default chain at least I don't think we use before_refresh for SSOCredentials. What use case were you thinking of?

[mullermp]

It's used by customers. My thought was we can make it a list of callbacks and not just one proc, then we can register a default one that also reread the token file instead of building it into refresh, but I don't know if we care to do that. It was just a thought.

[richardwang1124]

I think it looks good overall and changes to V4 are minor. Let me know if you end up keeping the options in the RefreshingIdentityProvider initializer.