- relationSubquery reads the pivot, key and table names from GORM's parsed
relationship (Schema.Relationships.Relations), never from a convention
- list search matches every relation column through a correlated EXISTS,
so the count query gains no JOIN and belongsToMany search stops failing
- sorting a hasMany or belongsToMany column orders by a correlated
string_agg subquery before the primary-key tiebreak
- polymorphic relations and unknown related columns answer 422
- DryRun smoke test TestListRelationSearchSmoke needs no Docker