Implement new Theme

* remove old SiteCustomization (deprecated)
* Create a theme and add a field for the header

plugin.rb

@@ -1,6 +1,6 @@
 # name: discourse-donations
 # about: Integrating Discourse with Stripe for donations
-# version: 1.7.3
+# version: 1.8.0
 # url: https://github.com/choiceaustralia/discourse-donations
 # authors: Rimian Perkins
 
@@ -13,16 +13,9 @@ enabled_site_setting :discourse_donations_enabled
 after_initialize do
   # Must be placed on every page for fraud protection.
   header_script = '<script src="https://js.stripe.com/v3/"></script>'
-
-  discourse_donations_customization = SiteCustomization.find_or_create_by({
-    name: 'Discourse Donations Header',
-    header: header_script,
-    mobile_header: header_script,
-    enabled: true,
-    user_id: -1
-  })
-
-  SiteCustomization.where(name: discourse_donations_customization.name).where.not(id: discourse_donations_customization.id).delete_all
+  discourse_donations_theme = Theme.find_or_create_by(name: 'Discourse Donations Header', hidden: false, user_id: -1)
+  discourse_donations_theme.set_field('common', 'head_tag', header_script)
+  discourse_donations_theme.save
 end
 
 Discourse::Application.routes.prepend do

spec/support/dd_helper.rb

@@ -1,3 +1,4 @@
+require 'fakeweb'
 
 #TODO register some fixtures