getKeyFromRequestData = requestData => {
  if (!requestData.key) {
    return Promise.reject(makeErrorObj('Key'));
  }

  if (!requestData.kind) {
    return Promise.reject(makeErrorObj('Kind'));
  }

  return datastore.key([requestData.kind, requestData.key]);
}
Gets a Datastore key from the kind/key pair in the request.

@param {object} requestData Cloud Function request data.
@param {string} requestData.key Datastore key string.
@param {string} requestData.kind Datastore kind.
@returns {object} Datastore key object.