- Removed Flow, flow is a nothing but options.
- Renamed Cacher to Storer.
- Removed the setter from the Transport. Store should do the initial set.
Getter is not removed, because extra fields are available through
Transport.Token.Extra(). It's not pleasant to implement a custom Storer
implementation to read such values.
oauth2: Remove VMs from the AppEngine example title
- Reduce the duplicate code by merging the flows and
determining the flow type by looking at the provided options.
- Options as a function type allows us to validate an individual
an option in its scope and makes it easier to compose the
built-in options with the third-party ones.