def add_recipient(recipient)
      raise 'Tried to add recipient to a non-group channel' unless group?
      raise ArgumentError, 'Tried to add a non-recipient to a group' unless recipient.is_a?(Recipient)

      @recipients << recipient
    end
def add_recipient(recipient)
      raise 'Tried to add recipient to a non-group channel' unless group?
      raise ArgumentError, 'Tried to add a non-recipient to a group' unless recipient.is_a?(Recipient)

      @recipients << recipient
    end
Adds a recipient to a group channel.
 @param recipient [Recipient] the recipient to add to the group
 @raise [ArgumentError] if tried to add a non-recipient
 @note For internal use only
 @!visibility private