New in version 10.4: This event replaces the
hook from the pibase plugin.
Allows to inject custom variables into the login form.
Deprecated since version 11.5: The interface
\TYPO3\CMS\Extbase\Mvc\View\ViewInterface has been deprecated
with v11.5 and will be removed with v12. This class's signature is set to change
TYPO3Fluid\Fluid\View\ViewInterface with the release v12.