4848b1e3aa
1. `POST /wp/v2/media`.
2. If the upload failed (HTTP 500 error), look for a response header with `X-WP-Upload-Attachment-ID` header that contains the newly created attachment ID.
3. `POST /wp/v2/media/{id}/post-process` with `{ "action": "create-image-subsizes" }`. This request may still fail, but it will save its progress.
4. On continued failure, `DELETE /wp/v2/media/{id}` to give up on the upload and instruct the user to resize their image before uploading.
Props TimothyBlynJacobs.
Fixes #47987.
git-svn-id: https://develop.svn.wordpress.org/trunk@46422 602fd350-edb4-49c9-b593-d223f7449a82