idea: make Update RPCs have a new proto field "path"

[toumorokoshi]

          create by necessity can't have a path in the request, at least not a required one: that would deviate in the case of server-generated fields.

In general apply is a simpler for that reason.

My idea would be to have path in the request, and the path in the resource always be output-only.

But I'll file a ticket on this.

Originally posted by @toumorokoshi in https://github.com/aep-dev/aep.dev/pull/115#discussion_r1524256213