Annotation Interface QVirtualField
Annotation to place onto fields in a QRecordEntity, to mark them as virtual
fields. Not as full featured (in this original implementation at least) as
QField, where many of the field's attributes can be set, and this can
be used to construct QFieldMetaData. Instead (at least for now), just
adding this here to address getting these passed back and forth when QRecord
and QRecordEntity objects are populated from one another.