[FRONT] Automatically send a request to check whether an e-mail/account number is in use.

[ArielMAJ]

Type of feature

🍕 Feature

Current behavior

The user only knows his e-mail is in use after fully filling the register form and submitting.

Suggested solution

• Add a request to GET: /user/check-email/{email} when the user stops typing its e-mail and show a warning saying it's already in use;
• Add a request to GET: /user/check-account-number/{accountNumber} when the user stops typing its account number and show a warning saying it's already in use;

Additional context

Endpoints already exist. They return: {"alreadyInUse": <BOOLEAN>}.