Validation implementation of `XMLStreamWriter` incomplete

[fasterxml]

Validation implementation of `XMLStreamWriter` incomplete

[cowtowncoder]

Correct, it has not (yet) been implemented. But it probably should not be lots of work to complete this, less than work to make reader-side validation work.

[cowtowncoder]

Actually only now realized that there is support, just not complete, and obviously not (well) tested.
But validator instance is passed; and we can perhaps use Stax2 test suite to help validate validation too...

[cowtowncoder]

After brief look, this is not trivial to add. Doable, certainly, but needs to dig in, compare how Woodstox it does (probably), and do it.

Also worth noting that since Aalto itself does not provide validators, nor Stax2 (although a ref impl might make sense?), users would need to write their own validator or use Woodstox-provided implementation. Tests here can do latter.