CAY-2842

Just noticed this merge:

https://github.com/apache/cayenne/pull/605/commits/99138fbcfe8f23e67805557bfcbca5bb452d8325

I noticed there are several "var" variables, such as:

    var orderDbAttribute = getOrderDbAttribute(nodeBuilder.build());

These won't compile with JDK 8 (introduced in 10). Did the minimum JDK
change to something higher? The documentation says: Cayenne 4.2 requires
JDK 1.8 or newer. Looks like 5.x will require JDK 11, so perhaps that's
what this is about?

If it is JDK 11+, do we want to allow "var" in the codebase? Makes it
harder to do code reviews (IMHO).

Thanks,
mrg