feat: Add dateUpdated field to Post model and update PostController

[baserrato]

This pull request includes changes to the devopsknowledgeshareapi package, introducing new features and enhancing existing ones. The changes mainly revolve around the addition of an AuthorController and updates to the Post and PostController classes. Furthermore, the PostRepository interface has been extended with new methods, and tests have been added or updated in the AuthorControllerTest and PostTest classes.

New Features:

• src/main/java/com/liatrio/dojo/devopsknowledgeshareapi/AuthorController.java: A new AuthorController class has been added which includes a getAuthors method that returns a list of authors.
• src/main/java/com/liatrio/dojo/devopsknowledgeshareapi/PostController.java: A putPost method has been added to the PostController class, allowing for updates to existing posts.

Updates to Existing Features:

• src/main/java/com/liatrio/dojo/devopsknowledgeshareapi/Post.java: The Post class has been updated with a new dateUpdated field, along with its corresponding setter and getter methods.
• src/main/java/com/liatrio/dojo/devopsknowledgeshareapi/PostRepository.java: The PostRepository interface has been extended with new methods to find posts by title, first name, and link.

Test Enhancements:

• src/test/java/com/liatrio/dojo/devopsknowledgeshareapi/AuthorControllerTest.java: A new test class AuthorControllerTest has been added to test the getAuthors method in the AuthorController class.
• src/test/java/com/liatrio/dojo/devopsknowledgeshareapi/PostTest.java: The PostTest class has been updated with a new test method setDateUpdatedTest to test the setDateUpdated method in the Post class.