docs: public MucConfigFormManager setMembersOnly(boolean isMembersOnly) throws MucConfigurationNotSupportedException {
          if (!supportsMembersOnly()) {
              throw new MucConfigurationNotSupportedException(MUC_ROOMCONFIG_MEMBERSONLY);
          }
          answerForm.setAnswer(MUC_ROOMCONFIG_MEMBERSONLY, isMembersOnly);
          return this;
      }