class Google::Cloud::Storage::File::SignerV4

def issuer_and_signer issuer, client_email, signing_key, private_key, signer
  issuer = determine_issuer issuer, client_email
  signing_key = determine_signing_key signing_key, private_key, signer
  signer = service_account_signer signing_key
  [issuer, signer]
end