protected static void addContact(UserID user, Scanner scan) {
assert (user != null);
System.out.println("Please enter username of the user you want to add: ");
String username = scan.next();
UserID userAboutToAdd = registeredUsers.get(username);
if (userAboutToAdd != null) {
user.addContact(username);
System.out.println("Contact added.");
} else System.out.println("Contact cannot be added, check make sure username is correct");
}
