Add ownerId property to Pet

src/main/java/org/springframework/samples/petclinic/mapper/PetMapper.java

 package org.springframework.samples.petclinic.mapper;
 
 import org.mapstruct.Mapper;
+import org.mapstruct.Mapping;
 import org.springframework.samples.petclinic.rest.dto.PetDto;
 import org.springframework.samples.petclinic.rest.dto.PetFieldsDto;
 import org.springframework.samples.petclinic.rest.dto.PetTypeDto;
@@ -14,6 +15,8 @@ import java.util.Collection;
  */
 @Mapper
 public interface PetMapper {
+
+    @Mapping(source = "owner.id", target = "ownerId")
     PetDto toPetDto(Pet pet);
 
     Collection<PetDto> toPetsDto(Collection<Pet> pets);

src/main/resources/openapi.yml

@@ -722,6 +722,14 @@ components:
               minimum: 0
               example: 1
               readOnly: true
+            ownerId:
+              title: Owner ID
+              description: The ID of the pet's owner.
+              type: integer
+              format: int32
+              minimum: 0
+              example: 1
+              readOnly: true
             visits:
               title: Visits
               description: Vet visit bookings for this pet.