remove MS-Author-Via header

[bourgeoa]

https://github.com/solid/node-solid-server/pull/1623 has been reverted due to mashlib and/or rdflib using MS-Author-Via header Should be removed following https://github.com/solid/specification/issues/124

[bourgeoa]

https://github.com/solid/solidos/issues/138. The problem could be :

• in rdflib https://github.com/linkeddata/rdflib.js/blob/12f6a20140aaa34d5e639f30050b568703635988/src/update-manager.ts#L106
• or in solid-panes https://github.com/solid/solid-panes/blob/83453fd8df41bad88fcab461fe4bcf52366035d6/src/profile/editProfile.view.ts#L99 with no distinction between false and undefined

[timbl]

You don't just switch from one form to another. You always have to have both for a while. Severs in the server-interim must provide both, and clients during the client-interim accept either. Interim periods of a year, for example, would be reasonable. Then when it changes to remove the old one from servers, then you upgrade the major version of the protocol. For example to 1.0.0 in the case of a protocol at 0.9

DO NOT REMOVE THE OLD ONE AT THIS STAGE

[RubenVerborgh]

The bigger problem seems to be the lack of N3 Patch support in rdflib, with the only support consisting of the non-standard SPARQL UPDATE. MS-Author-Via is just one part of the non-standard SPARQL UPDATE mechanism that rdflib relies on. So removing MS-Author-Via but leaving SPARQL UPDATE is at least somewhat arbitrary.