digest headers after IETF106: Validators and State-Changing methods

[Roberto Polli <[e-mail]>]

Hi @all,

and thanks for all the feedback provided on digest-headers after IETF106.

## Items we need WG guidance to move on

* Validators and Resources [0] [1] [2]: we need some help from editors
to clarify
  the relations b/w validators and digest.

* State-changing methods: we clarified Digest semantic for POST and PATCH.
   As 3230 states that digest is computed on complete representations we are
  not sure if we can extend this to all (eg. including future) methods
which may convey partial representations.
  Here
  - https://httpwg.org/http-extensions/ioggstream-952/digest-headers.html#resource-representation
  we analyze the impacts of method (eg. HEAD), metadata (eg.
content-type) and status code (eg. 204)
  on the payload body
  iiuc all those should be considered when discussing on digest.

* BNF Parameters https://github.com/httpwg/http-extensions/issues/850


## Quick win:

* Relationship with SRI https://github.com/httpwg/http-extensions/issues/868 :
   @Martin  if @Lucas 's considerations are enough for you, please close
   the issue you filed :)

## Closed after Singapore:

* Digest of Empty Representation: closed :)
https://github.com/httpwg/http-extensions/issues/849

## Deferred

- Use cases (drafted, to be done)
- Usage in signatures (I strongly support this)
- Threat model (deferred: maybe another I-D or dismiss)

[0]: https://github.com/httpwg/http-extensions/issues/936
[1]: https://github.com/httpwg/http-extensions/issues/949
[2]: https://github.com/httpwg/wg-materials/blob/gh-pages/ietf106/minutes.md#issues-936937--discussion-of-how-validators-specify-a-resource