Feature: #66709 - Add TemplateRootPaths support to Fluid/View/StandaloneView 

See forge#66709

Description 

The StandaloneView is extended with setTemplateRootPaths($templatePaths) and setTemplate($templateName, $throwException = TRUE). Now you can set a template by name.

When setTemplate($templateName) is called the $templateName is used to find the template in the given templateRootPaths with the same fallback logic as layoutRootPath and partialRootPath.

Basic example:

$view = GeneralUtility::makeInstance(StandaloneView::class);
$view->setLayoutRootPaths($layoutPaths);
$view->setPartialRootPaths($partialPaths);
$view->setTemplateRootPaths($templatePaths);

try {
	$view->setTemplate($templateName);
} catch (InvalidTemplateResourceException $e) {
	// no template $templateName found in given $templatePaths
	exit($e->getMessage());
}

$content = $view->render();
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Example of rendering an email template:

$view = GeneralUtility::makeInstance(StandaloneView::class);
$view->setLayoutRootPaths(array(GeneralUtility::getFileAbsFileName('EXT:my_extension/Resources/Private/Layouts')));
$view->setPartialRootPaths(array(GeneralUtility::getFileAbsFileName('EXT:my_extension/Resources/Private/Partials')));
$view->setTemplateRootPaths(array(GeneralUtility::getFileAbsFileName('EXT:my_extension/Resources/Private/Templates')));
$view->setTemplate('Email/Notification');

$emailBody = $view->render();
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Impact 

The public API of TYPO3\CMS\Fluid\View\StandaloneView is enhanced with the methods
setTemplateRootPaths($templatePaths) and setTemplate($templateName, $throwException = TRUE)