Currently, replies to inline-comments (comments on a given lines of files) are created using the POST /pull_requests/:id/inline-comments.

The problem is that we are forced to pass the file_path of the file the root comment is on. If this file has been renamed in the meantime, users are not able to post replies anymore and get a 404 - File not found error.

Files renames are not cheap to detect, and there can be some unknown edge cases if we tried to update the file_path whenever it changes.

The easiest solution would be to have a dedicated route `POST /pull_request_inline_comments/:id/reply` taking the id of a root comment to post replies. This way, we do not need to provide the file_path anymore.