false positive when eager loading a single record

[pcai]

safe query raises when eager loading on a resultset using #includes that only has a single related record. this is because activerecord doesnt generate an IN clause, but rather an equals clause. safe query doesnt recognize that the generated query is inherently bounded because the query is matching on a (unique) primary key.

the detection code should ideally figure out if the clause is equality matching on a unique column or pk so it doesnt throw on those queries