lazy_belongs_to produces redundant queries

[stokarenko]

There is a pretty useful jsonapi_use_foreign_key_on_belongs_to_relationship AMS setting:

When true, the relationship will determine its resource object identifier without calling the association or its serializer. This can be useful when calling the association object is triggering unnecessary queries.

It works pretty well for native belongs_to serializer's associations, but does not affect to lazy_belongs_to ones at the moment, producing redundant SQL queries.

Lazy relationship still turns N+1 into single query so the problem is not quite critical. In additional, has_one and has_many relationships will be loaded eventually. But still )