Document the WAC-Allow header in the spec.

[timbl]

This allows client code to be smart about whether to give the user editing interfaces to data or just view interfaces.

It also allows them to know whether it open to the public, which might affect for example, whether the user is invited to make a public link, like, bookmark, etc of the resource.

[RubenVerborgh]

A draft is at https://github.com/solid/solid-spec/blob/103b1e027356bd525e4cad0138e8288f4881df39/api-rest.md#wac-allow-headers

[timbl]

It says "If 'write' is present then 'append' should also be present." but "If write is present, Append is implied" would be more like the ACL spec, I thought.

[RubenVerborgh]

Agreed. It's not very normative at the moment, an explicit link to ACL should be made.

[csarven]

Transfering this issue to solid/specification . For the most part it is a duplicate of #170 but keeping it open for the time being.

[csarven]

Proposal/requirements merged via PR #210 . See further details/discussion on concerns of this header, as well as use cases for different permission groups. Implementation feedback is always useful/welcome. Please follow up with new issues/proposals.