session creation

app/controllers/sessions_controller.rb

@@ -3,6 +3,11 @@ class SessionsController < ApplicationController
   end
 
   def create
+    @user = User.find_by(username: params[:username])
+    if @user && @user.authenticate(params[:password])
+      sessions[:user_id] = @user.id
+    end
+    redirect_to '/welcome'
   end
 
   def welcome