message: properly handle optional `_json` property
  fixes
diff: @@ -41,11 +41,11 @@ export class Service {
  // TODO (EK): This is where we should look at req.user and see if we
  // can consolidate profiles. We might want to give the developer a hook
  // so that they can control the consolidation strategy.
  - profile._json.accessToken = accessToken;
  + const providerData = Object.assign({}, profile._json, {accessToken});
  let data = Object.assign({
  [`${options.provider}Id`]: profile.id,
  - [`${options.provider}`]: profile._json
  + [`${options.provider}`]: providerData
  });
  // If user found update and return them
  