You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: users_controller.rb
    path of file: ./repos/open-build-service/src/api/app/controllers/webui/groups
    
    the code of the file until where you have to start completion: module Webui
  modu
    
      def set_user
        @user = @group.users.find_by(login: params[:user_login])
        return if @user

        flash.now[:error] = "User '#{params[:user_login]}' not found in group '#{@group}'"
        render 'flash', status: :not_found
      end