Sidestep Devise "You are already logged in." error with Namespaced custom controllers and views

Question

This article explains how to let users make other users in devise. I've got it almost figured out, thanks to the answer provided in that article by Adam Waselnuk except I can't figure out how to create the same result with namespaced controllers and views. I get one of two errors, depending on how my routes.rb is set up... either Routing Error, No route matches [PUT] "/users/new" or

My code is below.

routes.rb

Rails.application.routes.draw do

  namespace :admin do
    resources :users, except: :create
  end
    post 'users/new' => 'admin/users#new', as: :create_user

  resources :shows
  resources :posts
  resources :global_posts

  devise_for :users, controllers: {
    registrations: "users/registrations",
    }


  root 'pages#home'

  get 'pages/home'
  get 'admin' => 'admin#index', as: :admin
end

admin/users_controller.rb

class Admin::UsersController < ApplicationController
  before_action :set_user, only: [:show, :edit, :update, :destroy]

  # GET /admin/users
  # GET /admin/users.json
  def index
    @all_users = User.all
  end

  def show
  end

  # GET /admin/users/new
  def new
    @user = User.new
  end

  # GET /admin/users/1/edit
  def edit
  end

  # POST /admin/users
  # POST /admin/users.json
  def create
    @user = User.new(user_params)
  end

  # PATCH/PUT /admin/users/1
  # PATCH/PUT /admin/users/1.json
  def update
    respond_to do |format|
      if @user.update(user_params)
        format.html { redirect_to @user, notice: 'User was successfully updated.' }
        format.json { render :show, status: :ok, location: @user }
      else
        format.html { render :edit }
        format.json { render json: @user.errors, status: :unprocessable_entity }
      end
    end
  end

  # DELETE /admin/users/1
  # DELETE /admin/users/1.json
  def destroy
    @user.destroy
    respond_to do |format|
      format.html { redirect_to root_path, notice: 'User was successfully destroyed.' }
      format.json { head :no_content }
    end
  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_user
      @user = User.find(params[:id])
    end

    # Never trust parameters from the scary internet, only allow the white list through.
    def user_params
      params.require(:user).permit(
      :name, :email, :password, :password_confirmation
      )
    end
end

And finally, the admin/users/new.html.erb

<h2>New User</h2>

<%= form_for @user, url: create_user_path, html: { method: :put } do |f| %>

  <div>
    <%= f.label :name %><br />
    <%= f.text_field :name, autofocus: true %>
  </div>

  <div>
    <%= f.label :email %><br />
    <%= f.email_field :email, autofocus: true %>
  </div>

  <div>
    <%= f.label :password %>
    <%= f.password_field :password, autocomplete: "off" %>
  </div>

  <div>
    <%= f.label :password_confirmation %><br />
    <%= f.password_field :password_confirmation, autocomplete: "off" %>
  </div>

  <div>
    <%= f.submit "Create New User" %>
  </div>

<% end %>

Answer 1

Your route should be

post 'users' => 'admin/users#create', as: :create_user

Then you can create the user in

def create
  @user = User.new(user_params)
  @user.save
end