public void validateChannel(String channelFromRequest, Channel channel) {
   if (!(Channel.isValid(channelFromRequest) && channel.name().equals(channelFromRequest))) {
     errors.add("Invalid channel %s", channelFromRequest);
   }
 }
 public void validateChannel(String channel) {
   if (!Channel.isValid(channel)) {
     errors.add("Invalid channel %s", channel);
   }
 }