FEATURE: store thumbnail algorithm version in optimized image table

Previously we had no idea what algorithm generated thumbnails, this starts tracking the version.

We also bumped up the version to force all optimized images to be generated. This is important cause we recently introduced pngquant which results in much smaller images.

spec/models/optimized_image_spec.rb

@@ -201,6 +201,32 @@ describe OptimizedImage do
 
   describe ".create_for" do
 
+    context "versioning" do
+      let(:filename) { 'logo.png' }
+      let(:file) { file_from_fixtures(filename) }
+
+      it "is able to update optimized images on version change" do
+        upload = UploadCreator.new(file, filename).create_for(Discourse.system_user.id)
+        optimized = OptimizedImage.create_for(upload, 10, 10)
+
+        expect(optimized.version).to eq(OptimizedImage::VERSION)
+
+        optimized_again = OptimizedImage.create_for(upload, 10, 10)
+        expect(optimized_again.id).to eq(optimized.id)
+
+        optimized.update_columns(version: nil)
+        old_id = optimized.id
+
+        optimized_new = OptimizedImage.create_for(upload, 10, 10)
+
+        expect(optimized_new.id).not_to eq(old_id)
+
+        # cleanup (which transaction rollback may miss)
+        optimized_new.destroy
+        upload.destroy
+      end
+    end
+
     it "is able to 'optimize' an svg" do
       # we don't really optimize anything, we simply copy
       # but at least this confirms this actually works