code: function get_user_account_id_for_credentials(username, password) {
  
      return new Promise((resolve, reject) => {
  
          dbMgr
              .find(app_config.get("app:db_collections:user_account"), {
                  "username": username,
                  "password": auth_util.encrypt_password(password)
              }, {"limit": 1})
              .then((accounts) => {
                  if (accounts.length > 0) {
                      return resolve(accounts[0]._id.toString());
                  } else {
                      return reject(new Error("Account not found."));
                  }
              }, reject);
      });
  }
docs: This is a demo implementaion of the process_signin_request() function
  that is required for the hapi-openid-connect plugin.  The implementaion must
  perform the following:
  
  
  1- verify that the username (email) and password match a user account record
  2- return a Promise that must resolve with the user account ID (string)
  
  The user profile must have a unique attirbute named _id, that has a toString()
  method, and it must be less than 255 characters (as per OpenID specs).
  
  
  @param  {[type]} username [description]
  @param  {[type]} password [description]
  @return {[type]}          [description]