FEATURE: generate (avatar) thumbnails in a background task

FIX: keep the "uploading..." indicator until the server replies via the MessageBus
FIX: text was disapearing when uploading an avatar

PERF: always use a region for S3 (defaults to 'us-east-1')
FEATURE: ApplyCDN middleware when using S3
FIX: use the same pattern to store files on S3 and locally
PERF: keep a local cache of uploads when generating thumbnails
FEATURE: migrate_to_s3 rake task

spec/controllers/uploads_controller_spec.rb

@@ -27,27 +27,35 @@ describe UploadsController do
       end
 
       it 'is successful with an image' do
+        Jobs.expects(:enqueue).with(:create_thumbnails, anything)
+
         message = MessageBus.track_publish do
-          xhr :post, :create, file: logo, type: "composer"
+          xhr :post, :create, file: logo, type: "avatar"
         end.first
 
         expect(response.status).to eq 200
 
-        expect(message.channel).to eq("/uploads/composer")
-        expect(message.data).to be
-      end
-
-      it 'is successful with an attachment' do
-        message = MessageBus.track_publish do
-          xhr :post, :create, file: text_file, type: "avatar"
-        end.first
-
-        expect(response.status).to eq 200
         expect(message.channel).to eq("/uploads/avatar")
         expect(message.data).to be
       end
 
+      it 'is successful with an attachment' do
+        SiteSetting.stubs(:authorized_extensions).returns("*")
+
+        Jobs.expects(:enqueue).never
+
+        message = MessageBus.track_publish do
+          xhr :post, :create, file: text_file, type: "composer"
+        end.first
+
+        expect(response.status).to eq 200
+        expect(message.channel).to eq("/uploads/composer")
+        expect(message.data).to be
+      end
+
       it 'correctly sets retain_hours for admins' do
+        Jobs.expects(:enqueue).with(:create_thumbnails, anything)
+
         log_in :admin
 
         message = MessageBus.track_publish do
@@ -61,6 +69,8 @@ describe UploadsController do
       it 'properly returns errors' do
         SiteSetting.stubs(:max_attachment_size_kb).returns(1)
 
+        Jobs.expects(:enqueue).never
+
         message = MessageBus.track_publish do
           xhr :post, :create, file: text_file, type: "avatar"
         end.first