Look into how requests with standard properties in <DAV:include> should be handled

[jwodder]

If an <DAV:include> tag in a PROPFIND request contains properties defined by the standard, is this any different than if they had not been listed in <DAV:include>? In particular, if <DAV:include> contains a standard property that the resource doesn't have, should that result in a 404 status for that property rather than the property just being omitted?

• For comparison, Apache's mod_dav seems to silently ignore standard properties in <DAV:include> regardless of whether a given resource has those properties defined.