DDSXTY14 — create_sample can't indicate failure

As defined create_sample can only return the sample object. This doesn't allow the API to indicate that there was an error unlike other calls in DDS. Other operations either can't normally fail, return an interface that can be null, or return a ReturnCode_t. At least in the C++ Language Mapping, create_sample can return a struct or a union by value, so it can't be null in those cases (section 5.11). I imagine this might be different in other mappings though.

Defer to next revision

Addressing this would require a change to teh DynamicData API which is mostly teh concern of the various Language Mappings

Doing it here can provide useful guidance to those language API. But we should coordinate this carefully to not cause unnecessary incompatibilities.

For this reasons I am recommending we defer to the next revision so we have more time to address this properly.