add entity type to solr

sdgs_helper.services.yml

services:
  sdgs_helper.twig.goals_count_extension:
    class: Drupal\sdgs_helper\Twig\GoalsCountExtension
    arguments: ['@config.factory']
    tags:
      - { name: twig.extension }

  sdgs_helper.solr_search_alter_documents:
    class: Drupal\sdgs_helper\EventSubscriber\SearchAlterDocuments
    tags:
      - { name: 'event_subscriber' }

SearchAlterDocuments.php

<?php
#web/modules/custom/sdgs_helper/src/EventSubscriber/SearchAlterDocuments.php

namespace Drupal\sdgs_helper\EventSubscriber;

use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Drupal\search_api_solr\Event\SearchApiSolrEvents;
use Drupal\search_api_solr\Event\PostCreateIndexDocumentEvent;

class SearchAlterDocuments implements EventSubscriberInterface {

    /**
   * {@inheritdoc}
   */
  public static function getSubscribedEvents(): array {
    return [
      SearchApiSolrEvents::POST_CREATE_INDEX_DOCUMENT => 'postCreateIndexDocuments',
    ];
  }

  /**
   * {@inheritdoc}
   */
  public function postCreateIndexDocuments(PostCreateIndexDocumentEvent $event): void {
    // Add a "foo" field with value "bar" to the document.
    $document = $event->getSolariumDocument();
    $document_fields = $document->getFields();
    
    if ($document['ss_type'] == 'partnerships' && !empty($document['fts_field_entity_types'])) {

        $fields = \Drupal::service('entity_field.manager')->getFieldDefinitions('node', 'partnerships');
        if (array_key_exists('field_entity_types', $fields)) {
            /** @var \Drupal\field\Entity\FieldConfig $fieldConfig */
            $fieldConfig = $fields['field_entity_types'];
            $allowedValues = $fieldConfig->getSetting('allowed_values');
        }
        if (!empty($allowedValues[$document['fts_field_entity_types']])) {
            $document->setField('sm_field_entity_types_name', $allowedValues[$document['fts_field_entity_types']]);
        }
    }
   
  }

}