Encode Content-Disposition filenames

Users downloading non-ASCII attachments would see garbled characters. When used with object storage, AWS S3 would return an InvalidArgument error: Header value cannot be represented using ISO-8859-1.

Per RFC 5987 and RFC 6266, Content-Disposition should be encoded properly. This commit takes the Rails 6 implementation of ActiveSuppport::Http::ContentDisposition (https://github.com/rails/rails/pull/33829) and ports it here.

However, due to gitlab-workhorse#207 (closed), the UTF-8 encoded Content-Disposition doesn't actually get sent to the user. This MR at least fixes AWS S3 access.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/47673

spec/controllers/concerns/send_file_upload_spec.rb

@@ -57,10 +57,12 @@ def dynamic_segment
       let(:params) { { attachment: filename } }
 
       it 'sends a file with content-type of text/plain' do
+        # Notice the filename= is omitted from the disposition; this is because
+        # Rails 5 will append this header in send_file
         expected_params = {
           content_type: 'text/plain',
           filename: 'test.js',
-          disposition: "attachment; filename=\"test.js\"; filename*=UTF-8''test.js"
+          disposition: "attachment; filename*=UTF-8''test.js"
         }
         expect(controller).to receive(:send_file).with(uploader.path, expected_params)
 
@@ -70,10 +72,12 @@ def dynamic_segment
       context 'with non-ASCII encoded filename' do
         let(:filename) { 'テスト.txt' }
 
+        # Notice the filename= is omitted from the disposition; this is because
+        # Rails 5 will append this header in send_file
         it 'sends content-disposition for non-ASCII encoded filenames' do
           expected_params = {
             filename: filename,
-            disposition: "attachment; filename=\"%3F%3F%3F.txt\"; filename*=UTF-8''%E3%83%86%E3%82%B9%E3%83%88.txt"
+            disposition: "attachment; filename*=UTF-8''%E3%83%86%E3%82%B9%E3%83%88.txt"
           }
           expect(controller).to receive(:send_file).with(uploader.path, expected_params)