code: function findUserFromAccessToken(accessToken, UserModel) {
  
      if (!accessToken) return null;
  
      return UserModel.findById(accessToken.userId).then((user) => {
          if (!user) return Promise.reject('No user with this access token was found.');
          return Promise.resolve(user);
      });
  }
docs: Finds a user from an access token
  @param {*} accessToken
  @param {*} UserModel