fix entity query to use unflattened DTO

[ruddell]

In the example:

entity Department
entity Location
relationship OneToOne {
  Department{location} to Location
}
dto * with mapstruct

DTOs are now unflattend (in #12947). Instead of calling for this.locationService.find(department.locationId), we should call this.locationService.find(department.location.id).

Fix #13080

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[ruddell]

Bounty claimed https://opencollective.com/generator-jhipster/expenses/28238

[pascalgrimaud]

thanks for the fix !
@ruddell : approved