DefaultAuth will search for a valid service account key or token in several locations.

KeyAuth configures the key flow and returns an http.RoundTripper that can be used to make authenticated requests using an access token The KeyFlow requires a service account key and a private key.

NoAuth configures a flow without authentication and returns an http.RoundTripper that can be used to make unauthenticated requests.

SetupAuth sets up authentication based on the configuration.

TokenAuth configures the token flow and returns an http.RoundTripper that can be used to make authenticated requests using a token.