FIX: Check for group name availability should skip reserved usernames.

app/controllers/groups_controller.rb

@@ -3,6 +3,7 @@ class GroupsController < ApplicationController
     :set_notifications,
     :mentionable,
     :messageable,
+    :check_name,
     :update,
     :histories,
     :request_membership,
@@ -314,6 +315,12 @@ class GroupsController < ApplicationController
     end
   end
 
+  def check_name
+    group_name = params.require(:group_name)
+    checker = UsernameCheckerService.new(allow_reserved_username: true)
+    render json: checker.check_username(group_name, nil)
+  end
+
   def remove_member
     group = Group.find_by(id: params[:id])
     raise Discourse::NotFound unless group