UserHelper fails with "Cannot find template named 'icon'" in version 15.1.2

[egonher]

Bug Report: UserHelper fails with "Cannot find template named 'icon'" in version 15.1.2

Version: 15.1.2

Issue:
After upgrading from 15.1.1 to 15.1.2, the login page with 'Users.Social.login' => true, throws:
InvalidArgumentException: Cannot find template named 'icon'

Root Cause:
The UserHelper now uses StringTemplateTrait but the templates defined in $_defaultConfig are not being loaded into the templater unless the helper is explicitly loaded in AppView.

Workaround:
Add to src/View/AppView.php:

public function initialize(): void
{
    parent::initialize();
    $this->loadHelper('CakeDC/Users.User');
}