def call
      return broadcast(:invalid) unless membership
      return broadcast(:invalid) if membership.role.to_s != "requested"

      transaction do
        send_notification
        reject_membership
      end

      broadcast(:ok, @user_group)
    end
def call
      return broadcast(:invalid) unless membership
      return broadcast(:invalid) if membership.role.to_s != "requested"

      transaction do
        send_notification
        reject_membership
      end

      broadcast(:ok, @user_group)
    end
Public: Initializes the command.

 membership - the UserGroupMembership to be accepted.
 Executes the command. Broadcasts these events:

 - :ok when everything is valid.
 - :invalid if we couldn't proceed.

 Returns nothing.