[TASK] Add deprecation message for old PluginRenderer

Classes/Hooks/PageLayoutView/PluginRenderer.php

@@ -32,6 +32,7 @@ use TYPO3\CMS\Fluid\View\StandaloneView;
  * Renders back-end preview for the SG Vimeo Videos plugin
  *
  * @package SGalinski\SgVimeo\Hooks
+ * @deprecated All of this class will be removed when TYPO3 10 support is dropped
  */
 class PluginRenderer implements PageLayoutViewDrawItemHookInterface {
 	/**
@@ -44,6 +45,7 @@ class PluginRenderer implements PageLayoutViewDrawItemHookInterface {
 	 * @param array $row Record row of tt_content
 	 * @return void
 	 * @noinspection ReferencingObjectsInspection
+	 * @deprecated All of this class will be removed when TYPO3 10 support is dropped
 	 */
 	public function preProcess(
 		PageLayoutView &$parentObject,
@@ -52,6 +54,11 @@ class PluginRenderer implements PageLayoutViewDrawItemHookInterface {
 		&$itemContent,
 		array &$row
 	): void {
+		trigger_error(
+			'Using the old style of rendering backend previews is deprecated and will not longer work when TYPO3 10'
+			. ' support is dropped! Please switch to using the Fluid Based Page Module instead!',
+			E_USER_DEPRECATED
+		);
 		if ($row['list_type'] === 'sgvimeo_vimeo') {
 			$drawItem = FALSE;