Change Principal to @AuthenticationPrincipal

[tarcidio]

@AuthenticationPrincipal in Spring Security is a best practice for accessing the authenticated user's details in a clean, type-safe, and readable manner. It simplifies the code by eliminating the need for manual retrieval and casting of the principal, making the controller methods more concise and easier to understand.

Example:

@GetMapping("/user")
public String getUser(@AuthenticationPrincipal UserDetails userDetails) {
    return "Hello, " + userDetails.getUsername();
}