New User
<%= simple_form_for(@user, url: users_path(@user)) do |f| %>
<%= f.error_notification %>
<%= f.input :username %>
<%= f.input :email %>
<%= f.input :password %>
<%= f.input :password_confirmation %>
<%= f.button :submit, class: "btn btn-primary" %>
<%= link_to 'Back', root_path, class: "btn" %>
<% end %>