FEATURE: Include optimized thumbnails for topics (#9215)

This introduces new APIs for obtaining optimized thumbnails for topics. There are a few building blocks required for this:

- Introduces new `image_upload_id` columns on the `posts` and `topics` table. This replaces the old `image_url` column, which means that thumbnails are now restricted to uploads. Hotlinked thumbnails are no longer possible. In normal use (with pull_hotlinked_images enabled), this has no noticeable impact

- A migration attempts to match existing urls to upload records. If a match cannot be found then the posts will be queued for rebake

- Optimized thumbnails are generated during post_process_cooked. If thumbnails are missing when serializing a topic list, then a sidekiq job is queued

- Topic lists and topics now include a `thumbnails` key, which includes all the available images:
   ```
   "thumbnails": [
   {
     "max_width": null,
     "max_height": null,
     "url": "//example.com/original-image.png",
     "width": 1380,
     "height": 1840
   },
   {
     "max_width": 1024,
     "max_height": 1024,
     "url": "//example.com/optimized-image.png",
     "width": 768,
     "height": 1024
   }
   ]
  ```

- Themes can request additional thumbnail sizes by using a modifier in their `about.json` file:
   ```
    "modifiers": {
      "topic_thumbnail_sizes": [
        [200, 200],
        [800, 800]
      ],
      ...
  ```
  Remember that these are generated asynchronously, so your theme should include logic to fallback to other available thumbnails if your requested size has not yet been generated

- Two new raw plugin outlets are introduced, to improve the customisability of the topic list. `topic-list-before-columns` and `topic-list-before-link`

spec/components/cooked_post_processor_spec.rb

@@ -751,16 +751,16 @@ describe CookedPostProcessor do
       end
 
       context "topic image" do
-        let(:post) { Fabricate(:post_with_uploaded_image) }
+        fab!(:post) { Fabricate(:post_with_uploaded_image) }
         let(:cpp) { CookedPostProcessor.new(post) }
 
         it "adds a topic image if there's one in the first post" do
           FastImage.stubs(:size)
-          expect(post.topic.image_url).to eq(nil)
+          expect(post.topic.image_upload_id).to eq(nil)
 
           cpp.post_process
           post.topic.reload
-          expect(post.topic.image_url).to be_present
+          expect(post.topic.image_upload_id).to be_present
         end
 
         it "removes image if post is edited and no longer has an image" do
@@ -768,14 +768,14 @@ describe CookedPostProcessor do
 
           cpp.post_process
           post.topic.reload
-          expect(post.topic.image_url).to be_present
-          expect(post.image_url).to be_present
+          expect(post.topic.image_upload_id).to be_present
+          expect(post.image_upload_id).to be_present
 
           post.update!(raw: "This post no longer has an image.")
           CookedPostProcessor.new(post).post_process
           post.topic.reload
-          expect(post.topic.image_url).not_to be_present
-          expect(post.image_url).not_to be_present
+          expect(post.topic.image_upload_id).not_to be_present
+          expect(post.image_upload_id).not_to be_present
         end
 
         it "won't remove the original image if another post doesn't have an image" do
@@ -784,15 +784,32 @@ describe CookedPostProcessor do
 
           cpp.post_process
           topic.reload
-          expect(topic.image_url).to be_present
-          expect(post.image_url).to be_present
+          expect(topic.image_upload_id).to be_present
+          expect(post.image_upload_id).to be_present
 
           post = Fabricate(:post, topic: topic, raw: "this post doesn't have an image")
           CookedPostProcessor.new(post).post_process
           topic.reload
 
-          expect(post.topic.image_url).to be_present
-          expect(post.image_url).to be_blank
+          expect(post.topic.image_upload_id).to be_present
+          expect(post.image_upload_id).to be_blank
+        end
+
+        it "generates thumbnails correctly" do
+          FastImage.expects(:size).returns([1750, 2000])
+
+          topic = post.topic
+          cpp.post_process
+          topic.reload
+          expect(topic.image_upload_id).to be_present
+          expect(post.image_upload_id).to be_present
+
+          post = Fabricate(:post, topic: topic, raw: "this post doesn't have an image")
+          CookedPostProcessor.new(post).post_process
+          topic.reload
+
+          expect(post.topic.image_upload_id).to be_present
+          expect(post.image_upload_id).to be_blank
         end
       end
 
@@ -802,10 +819,10 @@ describe CookedPostProcessor do
 
         it "adds a post image if there's one in the post" do
           FastImage.stubs(:size)
-          expect(reply.image_url).to eq(nil)
+          expect(reply.image_upload_id).to eq(nil)
           cpp.post_process
           reply.reload
-          expect(reply.image_url).to be_present
+          expect(reply.image_upload_id).to be_present
         end
       end
     end

spec/components/search_spec.rb

@@ -1134,13 +1134,11 @@ describe Search do
 
     it 'can find posts with images' do
       post_uploaded = Fabricate(:post_with_uploaded_image)
-      post_with_image_urls = Fabricate(:post_with_image_urls)
       Fabricate(:post)
 
       CookedPostProcessor.new(post_uploaded).update_post_image
-      CookedPostProcessor.new(post_with_image_urls).update_post_image
 
-      expect(Search.execute('with:images').posts.map(&:id)).to contain_exactly(post_uploaded.id, post_with_image_urls.id)
+      expect(Search.execute('with:images').posts.map(&:id)).to contain_exactly(post_uploaded.id)
     end
 
     it 'can find by latest' do

spec/components/topic_view_spec.rb

@@ -708,9 +708,12 @@ describe TopicView do
   end
 
   describe '#image_url' do
-    let!(:post1) { Fabricate(:post, topic: topic) }
-    let!(:post2) { Fabricate(:post, topic: topic) }
-    let!(:post3) { Fabricate(:post, topic: topic).tap { |p| p.update_column(:image_url, "post3_image.png") }.reload }
+    fab!(:op_upload) { Fabricate(:image_upload) }
+    fab!(:post3_upload) { Fabricate(:image_upload) }
+
+    fab!(:post1) { Fabricate(:post, topic: topic) }
+    fab!(:post2) { Fabricate(:post, topic: topic) }
+    fab!(:post3) { Fabricate(:post, topic: topic).tap { |p| p.update_column(:image_upload_id, post3_upload.id) }.reload }
 
     def topic_view_for_post(post_number)
       TopicView.new(topic.id, evil_trout, post_number: post_number)
@@ -718,14 +721,14 @@ describe TopicView do
 
     context "when op has an image" do
       before do
-        topic.update_column(:image_url, "op_image.png")
-        post1.update_column(:image_url, "op_image.png")
+        topic.update_column(:image_upload_id, op_upload.id)
+        post1.update_column(:image_upload_id, op_upload.id)
       end
 
       it "uses the topic image as a fallback when posts have no image" do
-        expect(topic_view_for_post(1).image_url).to eq("op_image.png")
-        expect(topic_view_for_post(2).image_url).to eq("op_image.png")
-        expect(topic_view_for_post(3).image_url).to eq("post3_image.png")
+        expect(topic_view_for_post(1).image_url).to eq(op_upload.url)
+        expect(topic_view_for_post(2).image_url).to eq(op_upload.url)
+        expect(topic_view_for_post(3).image_url).to eq(post3_upload.url)
       end
     end
 
@@ -733,7 +736,7 @@ describe TopicView do
       it "returns nil when posts have no image" do
         expect(topic_view_for_post(1).image_url).to eq(nil)
         expect(topic_view_for_post(2).image_url).to eq(nil)
-        expect(topic_view_for_post(3).image_url).to eq("post3_image.png")
+        expect(topic_view_for_post(3).image_url).to eq(post3_upload.url)
       end
     end
   end