[BUGFIX] Use BootCompletedEvent to register icons

In TYPO3 v13 it's still not possible to use the more
appropriate extension method to register icons, because
extension can instantiate IconRegistry inside ext_localconf.php
files.

This is now deprecated in v13 and we can switch to the
extension method in TYPO3 v14.

Fixes: #215
(cherry picked from commit 1db5b5c)

Classes/ServiceProvider.php

@@ -69,6 +69,7 @@ public function getFactories(): array
             'content-blocks.parent-field-names' => static::getContentBlockParentFieldNames(...),
             'content-blocks.add-typoscript' => static::addTypoScript(...),
             'content-blocks.add-user-tsconfig' => static::addUserTsConfig(...),
+            'content-blocks.register-icons' => static::configureIconRegistry(...),
             'content-blocks.hide-content-element-children' => static::hideContentElementChildren(...),
             'content-blocks.record-summary-for-localization' => static::recordSummaryForLocalization(...),
             'content-blocks.base-simple-tca-schema' => static::baseSimpleTcaSchema(...),
@@ -79,7 +80,6 @@ public function getFactories(): array
     public function getExtensions(): array
     {
         return [
-            IconRegistry::class => static::configureIconRegistry(...),
             PageDoktypeRegistry::class => static::configurePageTypes(...),
             ListenerProvider::class => static::addEventListeners(...),
         ] + parent::getExtensions();
@@ -329,22 +329,24 @@ public static function recordSummaryForLocalization(ContainerInterface $containe
         };
     }
 
-    public static function configureIconRegistry(ContainerInterface $container, IconRegistry $iconRegistry): IconRegistry
+    public static function configureIconRegistry(ContainerInterface $container): \Closure
     {
-        $iconsFromPackages = $container->get('content-blocks.icons');
-        foreach ($iconsFromPackages as $icon => $options) {
-            $provider = $options['provider'] ?? null;
-            unset($options['provider']);
-            $options ??= [];
-            if ($provider === null && ($options['source'] ?? false)) {
-                $provider = $iconRegistry->detectIconProvider($options['source']);
-            }
-            if ($provider === null) {
-                continue;
+        return static function (BootCompletedEvent $event) use ($container) {
+            $iconRegistry = $container->get(IconRegistry::class);
+            $iconsFromPackages = $container->get('content-blocks.icons');
+            foreach ($iconsFromPackages as $icon => $options) {
+                $provider = $options['provider'] ?? null;
+                unset($options['provider']);
+                $options ??= [];
+                if ($provider === null && ($options['source'] ?? false)) {
+                    $provider = $iconRegistry->detectIconProvider($options['source']);
+                }
+                if ($provider === null) {
+                    continue;
+                }
+                $iconRegistry->registerIcon($icon, $provider, $options);
             }
-            $iconRegistry->registerIcon($icon, $provider, $options);
-        }
-        return $iconRegistry;
+        };
     }
 
     public static function configurePageTypes(ContainerInterface $container, PageDoktypeRegistry $pageDoktypeRegistry): PageDoktypeRegistry
@@ -365,6 +367,7 @@ public static function configurePageTypes(ContainerInterface $container, PageDok
     public static function addEventListeners(ContainerInterface $container, ListenerProvider $listenerProvider): ListenerProvider
     {
         $listenerProvider->addListener(BootCompletedEvent::class, 'content-blocks.add-typoscript');
+        $listenerProvider->addListener(BootCompletedEvent::class, 'content-blocks.register-icons');
         $listenerProvider->addListener(BeforeLoadedUserTsConfigEvent::class, 'content-blocks.add-user-tsconfig');
         $listenerProvider->addListener(ModifyDatabaseQueryForContentEvent::class, 'content-blocks.hide-content-element-children');
         $listenerProvider->addListener(AfterRecordSummaryForLocalizationEvent::class, 'content-blocks.record-summary-for-localization');