function isTrue(data) {
                  return data.toLowerCase() === 'true';
                }
@operation add_board_member
@tag Boards

@summary Add New Board Member with Role

@description Only the admin user (the first user) can call the REST API.

**Note**: see [Boards.set_board_member_permission](#set_board_member_permission)
to later change the permissions.

@param {string} boardId the board ID
@param {string} userId the user ID
@param {string} action the action (needs to be `add`)
@param {boolean} isAdmin is the user an admin of the board
@param {boolean} isNoComments disable comments
@param {boolean} isCommentOnly only enable comments
@param {boolean} isWorker is the user a board worker
@return_type {_id: string,
              title: string}