add users controller and intermediate username step

app/controllers/users_controller.rb

@@ -0,0 +1,31 @@
+class UsersController < ApplicationController
+  before_action :set_user, only: [:edit, :update]
+
+  # GET /users/1/edit
+  def edit
+  end
+
+  # PATCH/PUT /users/1
+  # PATCH/PUT /users/1.json
+  def update
+    if @user.update(user_params)
+      redirect_to controller: 'landing', action: 'room', name: @user.username
+    else
+      render :edit
+    end
+  end
+
+  private
+    # Use callbacks to share common setup or constraints between actions.
+    def set_user
+      @user = User.find(params[:id])
+      if @user.username
+        raise ActionController::RoutingError.new('Not Found')
+      end
+    end
+
+    # Never trust parameters from the scary internet, only allow the white list through.
+    def user_params
+      params.require(:user).permit(:username)
+    end
+end