Add post-update hook to install the new entities.

islandora_hocr.post_update.php

@@ -0,0 +1,29 @@
+<?php
+
+/**
+ * @file
+ * Post-update hooks.
+ */
+
+use Symfony\Component\Yaml\Yaml;
+
+/**
+ * Install initial request handler and field type if they do not yet exist.
+ */
+function islandora_hocr_post_update_install_initial_entities() {
+  $ids = [
+    'search_api_solr.solr_field_type.islandora_hocr_und_7_0_0',
+    'search_api_solr.solr_request_handler.request_handler_select_islandora_hocr_7_0_0',
+  ];
+
+  $config_dir = \Drupal::service('extension.list.module')->getPath('islandora_hocr') . '/config/install';
+
+  foreach ($ids as $id) {
+    $data = Yaml::parseFile("{$config_dir}/{$id}.yml");
+    $config = \Drupal::configFactory()->getEditable($id);
+    if ($config->isNew()) {
+      $config->initWithData($data)->save(TRUE);
+    }
+  }
+
+}