discourse/app/controllers/groups_controller.rb

class GroupsController < ApplicationController

  def show
    group = Group.where(name: params.require(:id)).first
    guardian.ensure_can_see!(group)
    render_serialized(group, BasicGroupSerializer)
  end

  def members
    group = Group.where(name: params.require(:group_id)).first
    guardian.ensure_can_see!(group)
    render_serialized(group.users.order('username_lower asc').limit(200).to_a, GroupUserSerializer)
  end

end