Move custom pages form partial to a component

This way changing it will be easier.

Note we're changing the name of the HTML class to follow our naming
conventions; the `edit_page` class wasn't used anywhere, so we don't
need to change anything else.

app/components/admin/site_customization/pages/edit_component.html.erb

@@ -11,4 +11,4 @@
   ) %>
 <% end %>
 
-<%= render "form" %>
+<%= render Admin::SiteCustomization::Pages::FormComponent.new(page) %>

app/components/admin/site_customization/pages/form_component.html.erb

@@ -1,7 +1,7 @@
-<%= render "shared/globalize_locales", resource: @page %>
+<%= render "shared/globalize_locales", resource: page %>
 
-<%= translatable_form_for [:admin, @page], html: { class: "edit_page" } do |f| %>
-  <%= render "shared/errors", resource: @page %>
+<%= translatable_form_for [:admin, page], html: { class: "site-customization-pages-form" } do |f| %>
+  <%= render "shared/errors", resource: page %>
 
   <div class="row">
     <div class="small-12 column">

app/components/admin/site_customization/pages/form_component.rb

@@ -0,0 +1,9 @@
+class Admin::SiteCustomization::Pages::FormComponent < ApplicationComponent
+  include TranslatableFormHelper
+  include GlobalizeHelper
+  attr_reader :page
+
+  def initialize(page)
+    @page = page
+  end
+end

app/components/admin/site_customization/pages/new_component.html.erb

@@ -3,4 +3,4 @@
 
 <%= header %>
 
-<%= render "form" %>
+<%= render Admin::SiteCustomization::Pages::FormComponent.new(page) %>