VavaHelper/Vava-API

AI Summary: Implement error handling for the user registration endpoint to prevent duplicate email addresses. The endpoint should return a 409 Conflict HTTP status code with a JSON body indicating the email already exists if a user attempts to register with an existing email address.

AI Summary: Modify the Spring Boot authentication API's password reset functionality to generate and send email links that redirect to a frontend URL for password reset instead of the API endpoint itself. This involves updating the `createPasswordResetToken` method in the `PasswordResetService` to construct the URL using a configurable frontend URL (potentially from `application.properties`).

AI Summary: The task is to modify the `createPasswordResetToken` method in the `PasswordResetService` class. The current implementation doesn't handle expired tokens correctly; it should either update the existing expired token with a new one or delete the expired token and create a new one. The goal is to allow users to generate a new password reset token if their previous token has expired.