Remove PetRepository and use Owner as aggregate

Owner is really the aggregate root in DDD terms and there is no
need to directly access the Pet entity.

src/main/resources/templates/pets/createOrUpdatePetForm.html

@@ -13,7 +13,7 @@
       <div class="form-group">
         <label class="col-sm-2 control-label">Owner</label>
         <div class="col-sm-10">
-          <span th:text="${pet.owner?.firstName + ' ' + pet.owner?.lastName}" />
+          <span th:text="${owner?.firstName + ' ' + owner?.lastName}" />
         </div>
       </div>
       <input

src/main/resources/templates/pets/createOrUpdateVisitForm.html

@@ -24,7 +24,7 @@
         th:text="${#temporals.format(pet.birthDate, 'yyyy-MM-dd')}"></td>
       <td th:text="${pet.type}"></td>
       <td
-        th:text="${pet.owner?.firstName + ' ' + pet.owner?.lastName}"></td>
+        th:text="${owner?.firstName + ' ' + owner?.lastName}"></td>
     </tr>
   </table>