iqdb: update API client to use new version of IQDB.

Replace the old IQDB API client with a new client for the new forked
version of IQDB at https://github.com/danbooru/iqdb.

Changes:

* The /iqdb_queries endpoint now returns `hash` and `signature` fields.
  The `signature` is the full decoded Haar signature, while the `hash`
  is a encoded version of the signature.
* The /iqdb_queries endpoint no longer returns `width` and `height`
  fields in the response (these were always 128x128).
* We no longer need the IQDBs frontend server, now we talk to the IQDB
  instance directly.
* We no longer send add/remove image commands to IQDB through AWS SQS,
  now we send them to IQDB directly. They are sent in a delayed job so
  that if IQDB is down, uploading images is still possible, the add
  image commands will just get queued up.
* Fix a bug where regenerating an image's thumbnails didn't regenerate
  IQDB, because IQDB silently ignored add image commands when the image
  already existed in the database.

test/functional/iqdb_queries_controller_test.rb

@@ -11,7 +11,7 @@ class IqdbQueriesControllerTest < ActionDispatch::IntegrationTest
       context "with a url parameter" do
         should "render a response" do
           @url = "https://google.com"
-          @matches = [{ "post_id" => @post.id, "width" => 128, "height" => 128, "score" => 95.0 }]
+          @matches = [{ post_id: @post.id, score: 95.0 }]
           mock_iqdb_matches(@matches)
 
           get_auth iqdb_queries_path, @user, as: :javascript, params: { url: @url }
@@ -22,10 +22,13 @@ class IqdbQueriesControllerTest < ActionDispatch::IntegrationTest
       end
 
       context "with a post_id parameter" do
-        should "redirect to iqdbs" do
-          @matches = [{ "post_id" => @post.id, "width" => 128, "height" => 128, "score" => 95.0 }]
+        should "render a response" do
+          @matches = [{ post_id: @post.id, score: 95.0 }]
           mock_iqdb_matches(@matches)
 
+          # Make the call to `@post.file(:preview)` work.
+          Post.any_instance.stubs(:file).returns(File.open("test/files/test.jpg"))
+
           get_auth iqdb_queries_path, @user, params: { post_id: @post.id }
 
           assert_response :success