E.g. projecting on "foo.bar" where "foo" is a flattened object field. This would require some extra work since we need to go through a tree when extracting the value from the hit (currently we naively assume the hit just contains a key -> value map of projections).

See also org.hibernate.search.v6poc.integrationtest.backend.tck.search.projection.SearchProjectionIT#field_inFlattenedObject, which should be re-enabled once we got this working.