should reject an scxml document containing data without @id
Created by: mattoshry
Per [1], data/@id is required.
SCION should reject the following:
<scxml xmlns="http://www.w3.org/2005/07/scxml"
version="1.0">
<datamodel>
<!-- missing id -->
<data/>
</datamodel>
<state id="uber">
<transition event="*" target="fail">
<log expr="'unhandled event ' + JSON.stringify(_event)"/>
</transition>
</state>
<final id="fail"/>
</scxml>```
[1] https://www.w3.org/TR/scxml/#data