Credentials with optional file locking caching feature whenever token refreshes

[junpeng-jp]

Feature Requested
A Credentials object with file locking read / write option that emulates the old google oauth2client's Storage and the post-refresh caching in Client

Potential Implementation

• a custom Credential object that has self.cache & modify before_request method (see here) to do some sort of caching every time a refresh occurs

Other Comments

• Happy to help add this feature to this repo but would like some guidance
• before_request is called in both the AuthorizedSession and AuthorizedHttp object's request method. I think this could be a good place to add some post-refresh functionality

[tswast]

@junpeng-jp This makes some sense to me, but I'd like to understand more. Is there a specific use case you have in mind / problem you're having that this would solve?

This package already has some capability for writing credentials to a file and reading them, so I'd like to understand where the gaps are in the current capabilities.