[!!!][FEATURE] Add new Events for Indexing

This change adds new PSR-14 events:

* `ApacheSolrForTypo3\Solr\Event\Indexing\BeforePageDocumentIsProcessedForIndexingEvent`
previously used with `$GLOBALS['TYPO3_CONF_VARS']['EXTCONF']['solr']['Indexer']['indexPageAddDocuments']`

* `ApacheSolrForTypo3\Solr\Event\Indexing\BeforeDocumentIsProcessedForIndexingEvent`
previously used with `$GLOBALS['TYPO3_CONF_VARS']['EXTCONF']['solr']['IndexQueueIndexer']['preAddModifyDocuments']`

* `ApacheSolrForTypo3\Solr\Event\Indexing\BeforeDocumentsAreIndexedEvent`
previously used with `$GLOBALS['TYPO3_CONF_VARS']['EXTCONF']['solr']['IndexQueueIndexer']['indexItemAddDocuments']`

This way, EXT:solr migrates to PSR-14 events and adds a more defined way to utilize the PHP API and to help extension authors to understand what is used in EXT:solr.

The hooks
* `$GLOBALS['TYPO3_CONF_VARS']['EXTCONF']['solr']['IndexQueueIndexer']['preAddModifyDocuments']`
* `$GLOBALS['TYPO3_CONF_VARS']['EXTCONF']['solr']['IndexQueueIndexer']['indexItemAddDocuments']`
* `$GLOBALS['TYPO3_CONF_VARS']['EXTCONF']['solr']['Indexer']['indexPageAddDocuments']`

are now removed in favor of the new events.

These interfaces related to the hooks are removed:
* `ApacheSolrForTypo3\Solr\IndexQueue\PageIndexerDocumentsModifier`
* `ApacheSolrForTypo3\Solr\IndexQueue\AdditionalIndexQueueItemIndexer`
* `ApacheSolrForTypo3\Solr\AdditionalPageIndexer`

Documentation is added, tests are adapted.

Relates: #3376, #3441
Fixes: #3437

Classes/Event/Indexing/BeforeDocumentIsProcessedForIndexingEvent.php

@@ -0,0 +1,83 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace ApacheSolrForTypo3\Solr\Event\Indexing;
+
+use ApacheSolrForTypo3\Solr\IndexQueue\Item;
+use ApacheSolrForTypo3\Solr\System\Solr\Document\Document;
+use TYPO3\CMS\Core\Site\Entity\Site;
+use TYPO3\CMS\Core\Site\Entity\SiteLanguage;
+
+/**
+ * Allows third party extensions to provide additional documents which
+ * should be indexed for the current item.
+ *
+ * Previously used with
+ * $GLOBALS['TYPO3_CONF_VARS']['EXTCONF']['solr']['IndexQueueIndexer']['indexItemAddDocuments']
+ */
+class BeforeDocumentIsProcessedForIndexingEvent
+{
+    /**
+     * @var Document[]
+     */
+    private array $documents = [];
+
+    public function __construct(
+        private readonly Document $document,
+        private readonly Site $site,
+        private readonly SiteLanguage $siteLanguage,
+        private readonly Item $indexQueueItem
+    ) {
+        $this->documents[] = $this->document;
+    }
+
+    public function getSite(): Site
+    {
+        return $this->site;
+    }
+
+    public function getSiteLanguage(): SiteLanguage
+    {
+        return $this->siteLanguage;
+    }
+
+    public function getIndexQueueItem(): Item
+    {
+        return $this->indexQueueItem;
+    }
+
+    public function getDocument(): Document
+    {
+        return $this->document;
+    }
+
+    /**
+     * @param Document[] $documents
+     */
+    public function addDocuments(array $documents): void
+    {
+        $this->documents = array_merge($this->documents, $documents);
+    }
+
+    /**
+     * @return Document[]
+     */
+    public function getDocuments(): array
+    {
+        return $this->documents;
+    }
+}

Classes/Event/Indexing/BeforeDocumentsAreIndexedEvent.php

@@ -0,0 +1,78 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace ApacheSolrForTypo3\Solr\Event\Indexing;
+
+use ApacheSolrForTypo3\Solr\IndexQueue\Item;
+use ApacheSolrForTypo3\Solr\System\Solr\Document\Document;
+use TYPO3\CMS\Core\Site\Entity\Site;
+use TYPO3\CMS\Core\Site\Entity\SiteLanguage;
+
+/**
+ * An event to manipulate documents right before they get added to the Solr index.
+ *
+ * Previously used with
+ * $GLOBALS['TYPO3_CONF_VARS']['EXTCONF']['solr']['IndexQueueIndexer']['preAddModifyDocuments']
+ */
+class BeforeDocumentsAreIndexedEvent
+{
+    public function __construct(
+        private readonly Document $document,
+        private readonly Site $site,
+        private readonly SiteLanguage $siteLanguage,
+        private readonly Item $indexQueueItem,
+        /**  @var Document[] */
+        private array $documents,
+    ) {
+    }
+
+    public function getSite(): Site
+    {
+        return $this->site;
+    }
+
+    public function getSiteLanguage(): SiteLanguage
+    {
+        return $this->siteLanguage;
+    }
+
+    public function getIndexQueueItem(): Item
+    {
+        return $this->indexQueueItem;
+    }
+
+    public function getDocument(): Document
+    {
+        return $this->document;
+    }
+
+    /**
+     * @param Document[] $documents
+     */
+    public function addDocuments(array $documents): void
+    {
+        $this->documents = array_merge($this->documents, $documents);
+    }
+
+    /**
+     * @return Document[]
+     */
+    public function getDocuments(): array
+    {
+        return $this->documents;
+    }
+}

Classes/Event/Indexing/BeforePageDocumentIsProcessedForIndexingEvent.php

@@ -0,0 +1,82 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace ApacheSolrForTypo3\Solr\Event\Indexing;
+
+use ApacheSolrForTypo3\Solr\IndexQueue\Item;
+use ApacheSolrForTypo3\Solr\System\Solr\Document\Document;
+use TYPO3\CMS\Core\Site\Entity\Site;
+use TYPO3\CMS\Core\Site\Entity\SiteLanguage;
+
+/**
+ * Allows to add more documents to the Solr index.
+ *
+ * Previously used with
+ * $GLOBALS['TYPO3_CONF_VARS']['EXTCONF']['solr']['Indexer']['indexPageAddDocuments']
+ */
+class BeforePageDocumentIsProcessedForIndexingEvent
+{
+    /**
+     * @var Document[]
+     */
+    private array $documents = [];
+
+    public function __construct(
+        private readonly Document $document,
+        private readonly Site $site,
+        private readonly SiteLanguage $siteLanguage,
+        private readonly Item $indexQueueItem
+    ) {
+        $this->documents[] = $this->document;
+    }
+
+    public function getSite(): Site
+    {
+        return $this->site;
+    }
+
+    public function getSiteLanguage(): SiteLanguage
+    {
+        return $this->siteLanguage;
+    }
+
+    public function getIndexQueueItem(): Item
+    {
+        return $this->indexQueueItem;
+    }
+
+    public function getDocument(): Document
+    {
+        return $this->document;
+    }
+
+    /**
+     * @param Document[] $documents
+     */
+    public function addDocuments(array $documents): void
+    {
+        $this->documents = array_merge($this->documents, $documents);
+    }
+
+    /**
+     * @return Document[]
+     */
+    public function getDocuments(): array
+    {
+        return $this->documents;
+    }
+}