Show UI warning to user when they need provider data but have not setup Synth yet (#1926)

* Simplify provider concerns

* Update tests

* Add UI warning for missing Synth key if family requires external data

app/models/upgrader/provided.rb

@@ -1,11 +1,14 @@
 module Upgrader::Provided
   extend ActiveSupport::Concern
-  include Providable
 
   class_methods do
     private
       def fetch_latest_upgrade_candidates_from_provider
         git_repository_provider.fetch_latest_upgrade_candidates
       end
+
+      def git_repository_provider
+        Provider::Github.new
+      end
   end
 end