-<modify>: remove `@Transactional`.
-<add>: create unit-test file related to `PetValidator`.
-<refactor>: move pet objects initialization to `@BeforeEach` setup.
Spring Boot 3.4 supports the webjars-locator-lite which in turn
supports native images, so we are back to versionless URLs for
webjars assets in templates.
<refactor>: remove useless logic cod.
<refactor>: detele useless annotation which is provided by Jpa.
<refactor>: refactor implement of `findByLastName`, use Jpa to simplify query.
-<replace>: use `JpaRepository` to replace `Repository` in `OwnerRepository` class.
-<remove1>: remove `save()` method. JpaRepository provides it by default.
-<remove2>: remove `@Query` because in `Owner` class, the `@OneToMany` annotiation achieved `fetch` in query.
-<refactor1>: use `Optional<Owner>` to recieve the result from `findById()`, and if is null, throw `IllegalArugmentExpection`.
-<refactor2>: achieve the assert to judge return value in tests.
-<add>: add name to `@author` tag.
-<add>: add `@NotBlank` validation to pet's name.
-<refactor>: delete useless code and add unit test to check duplicate Pet name validation logic.
-<modify>: add `Id` to pet in unit test.
-<refactor>: classify unit test.
<modify>: adjust code format.
- <optimize>: delete logic `add owner to model` because of the comment `@ModelAttribute("owner")`.
- <fix>: add logical judgment in ordet to avoid `owner` from `form` and `ownerId` from `url` mismatch.
- Update Spring Boot release, Checkstyle, Mysql.
- Formatting pom.xml with sortpom-maven-plugin.
- Rename README to standard file name.
- Adding GitHub Action for Gradle.
