Fix multipart attachments not uploading
Mixing and matching the use of Rack::Request and ActionDispatch::Request in Rails 5 is bad, particularly if you have middleware that manipulates or accesses environment variables.
Gitlab::Middleware::Multipart attempts to rewrite request parameters
to the proper values (e.g. replacing data_file with
UploadedFile). It does this by calling Rack::Request#update_params,
which essentially updates env['rack.request.form_hash'].
By changing to ActionDispatch::Request, the Go middleware was causing
the request parameters to be stored inside
env['action_dispatch.request.request_parameters']. Later calls to
Rack::Request#update_params would not have any effect because it would attempt to
update env['rack.request.form_has'] instead of
env['action_dispatch.request.request_parameters']. As a result, the
controller still saw the old parameters.
Since the Go middleware appears to be using ActionDispatch::Request
for authorization methods, we can switch the multipart middleware to
use it too.