Resumable Upload draft updates

Dear working group,

last week we published iteration -04 for the resumable upload draft [1],
which includes a number of useful additions:

   - The application/partial-upload media type for PATCH requests
   - Upload limits (max/min total size, max/min request size, upload
   expiration)
   - Guidelines for handling content and transfer codings
   - Guidelines for integrity checks using digest fields
   - Problem types for error responses

From our perspective as editors, the draft is shaping up well, but a few
small questions could still be addressed:


   1. The server announces the upload limits (e.g. for maximum size or
   minimum request size) only when the client creates a new upload resource.
   For the client it would also be useful to know these limits upfront before
   creating an upload. The client may then decide to not start an upload if it
   cannot obey the limits. Should we allow the client to send an OPTIONS
   request to retrieve the upload limits before creating a resource? [2]
   2. If an upload is spread across multiple requests (e.g. due to limits
   from intermediaries), the server only knows the upload length once the
   upload is completed. However, in many cases the client knows the length
   upfront and could indicate the length to the server, who can use this
   information to optimize the upload storage or reject the upload entirely.
   Should we add an advisory header to upload creation requests to indicate
   the upload length? The Upload-Complete header would still keep the
   authority for completing the upload. [3]
   3. A client may include integrity fields to send the expected digest for
   the upload to the server for later verification. This requires the client
   to know the digest upfront or transmit it later using trailers (which might
   not always be possible). Should we also provide a way for the client to
   request a digest from the server once the upload is complete? Then the
   client and server can compute the digest during the upload and the client
   can compare its digest to the server's. [4]

We are looking forward to discussing these points in the httpbis session on
Monday!

Best regards,
Marius Kleidl

[1]
https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-resumable-upload-04
[2] https://github.com/httpwg/http-extensions/issues/2833
[3] https://github.com/httpwg/http-extensions/issues/2832
[4] https://github.com/httpwg/http-extensions/issues/2834