Guest users are not working as expected

[AIC-BV]

As discussed on Discord with @mjauvin, guest users are currently not working.

I create a guest (documentation)

$user = Auth::registerGuest(['email' => $email]);

Assuming onCheckEmail is not an official part of the plugin but just an example; this can be ignored
I adjusted example the onCheckEmail() function because Auth::findUserByLogin returns TRUE if a user is found regardless of its value user->is_guest. In my case (and everyone elses?), it should also return FALSE if user->is_guest because even though the user already exists, the user with that specific e-mailadress is still available to be claimed by anyone.
I adjusted the function to solve this issue (which is not really an issue but not documented I guess).

~~public function onCheckEmail() {

        // keep isTaken
        $isTaken = 1;

        // get email
        $email = post('email');

        // search the user
        $user = Auth::findUserByLogin($email);

        // if user is NOT found or user is guest -> account is still available to claim
        if (!$user || $user->is_guest) $isTaken = 0;

        return ['isTaken' => $isTaken];

    }~~

This brings me to the next issue;
When the guest user finally wants to register, he gets a validation error that the e-mailadress is already in use because:

plugins/winter/user/components/Account.php (around line 295)
$rules = (new UserModel)->rules;

Which contains

plugins/winter/user/models/User.php
public $rules = [
        'email'    => 'required|between:6,255|email|unique:users',
        ...
];

but this should not ever happen because even though the user already exists and the e-mail is already taken, the e-mail can still be used to register the guest and claim the account in the process.

[AIC-BV]

This is also a bug related to guest users
#35