Const
TokenSource.endpoint creates a token source that fetches credentials from a given URL using the standard endpoint format: FIXME: add docs link here in the future!
TokenSource.literal contains a single, literal set of TokenSourceResponseObject credentials, either provided directly or returned from a provided function.
TokenSource.sandboxTokenServer queries a sandbox token server for credentials, which supports quick prototyping / getting started types of use cases.
This token provider is INSECURE and should NOT be used in production.
For more info:
TokenSource.custom allows a user to define a manual function which generates new TokenSourceResponseObject values on demand.
Use this to get credentials from custom backends / etc.