Rename and re-organise custom modules

- Rename `opd_talks` to `opdavies_talks`
- Rename `custom` to `opdavies_blog`

web/modules/custom/opdavies_blog/hooks/preprocess/block.inc

@@ -0,0 +1,18 @@
+<?php
+
+/**
+ * @file
+ * Block preprocess hooks.
+ */
+
+declare(strict_types=1);
+
+/**
+ * Implements hook_preprocess_HOOK().
+ */
+function opdavies_blog_preprocess_block(array &$variables): void {
+  // Add the 'markup' class to blocks.
+  if (in_array($variables['plugin_id'], ['views_block:featured_blog_posts-block_1'])) {
+    $variables['attributes']['class'][] = 'markup';
+  }
+}

web/modules/custom/opdavies_blog/hooks/preprocess/node.inc

@@ -0,0 +1,21 @@
+<?php
+
+/**
+ * @file
+ * Node preprocess functions.
+ */
+
+declare(strict_types=1);
+
+/**
+ * Implements hook_preprocess_HOOK().
+ */
+function opdavies_blog_preprocess_node(array &$variables): void {
+  if (!method_exists($variables['node'], 'getExternalLink')) {
+    return;
+  }
+
+  if ($link = $variables['node']->getExternalLink()) {
+    $variables['url'] = $link['uri'];
+  }
+}