@GetMapping(value = "/owners/*/pets/{petId}/visits/new")
    public String initNewVisitForm(@PathVariable("petId") int petId, Map<String, Object> model) {
        return "pets/createOrUpdateVisitForm";
    }
Called before each and every @GetMapping or @PostMapping annotated method.
2 goals:
- Make sure we always have fresh data
- Since we do not use the session scope, make sure that Pet object always has an id
(Even though id is not part of the form fields)

@param petId
@return Pet
src/main/java/org/springframework/samples/petclinic/web/VisitController.java