NewClientFromCredentialFile constructs a new Google Cloud API client from the supplied JSON credential file.

DisabledCredentialFile is a special value for the credential file path that we disable oauth authentication this is used for local testing.

ErrUnsupportedDatabaseVersion is returned when a user attempts to use db-auth-gateway with an incompatible database version.

Client is an instance of the cloud database api client for use with Google Cloud.

DisabledTokenSource is a mocked oauth token source for local testing.