class Google::Auth::ServiceAccountJwtHeaderCredentials

def apply! a_hash, opts = {}

The jwt token is used as the value of a 'Bearer '.

hash.
Construct a jwt token if the JWT_AUD_URI key is present in the input 
def apply! a_hash, opts = {}
  jwt_aud_uri = a_hash.delete JWT_AUD_URI_KEY
  return a_hash if jwt_aud_uri.nil? && @scope.nil?
  jwt_token = new_jwt_token jwt_aud_uri, opts
  a_hash[AUTH_METADATA_KEY] = "Bearer #{jwt_token}"
  logger&.debug do
    hash = Digest::SHA256.hexdigest jwt_token
    Google::Logging::Message.from message: "Sending JWT auth token. (sha256:#{hash})"
  end
  a_hash
end