Javadoc
Collect metadata for column that will be unwrapped to full entity in the final SQL
(possibly including joint prefetch).
This information will be used to correctly create Persistent object back from raw result.
This method is actually repeating logic of
org.apache.cayenne.access.translator.select.DefaultSelectTranslator#appendQueryColumns.
Here we don't care about intermediate joins and few other things so it's shorter.
Logic of these methods should be unified and simplified, possibly to a single source of metadata,
generated only once and used everywhere.