Remove multi-domain support on admin user pages

refs #166

app/controllers/admin/users_controller.rb

@@ -4,8 +4,7 @@ class Admin::UsersController < Admin::BaseController
 
   def index
     ldap   = LdapService.new
-    @ou    = params[:ou] || Setting.primary_domain
-    @orgs  = ldap.fetch_organizations
+    @ou    = Setting.primary_domain
     @pagy, @users = pagy(User.where(ou: @ou).order(cn: :asc))
 
     @stats = {
@@ -27,8 +26,8 @@ class Admin::UsersController < Admin::BaseController
   private
 
   def set_user
-    address = params[:address].split("@")
-    @user = User.where(cn: address.first, ou: address.last).first
+    @user = User.find_by(cn: params[:username], ou: Setting.primary_domain)
+    http_status :not_found unless @user
   end
 
   def set_current_section