Introduce "adapters"

Goals

• Being able to write adaptors that can perform BE logic and adapt Drupal field values to match props

Non-goals

• Good UX
• Any UI to change the expression used for a sourceType == dynamic prop value
• Nested adapters
• Translations
• API representation (JSON:API) or otherwise

MR contents

• ** New Adapter plugin type and AdapterManager service **. Each plugin can:
  1. addInput(string $input, mixed $itemBase) - adds input to adapter instance
  2. adapt() - adapts output
  3. outputSchemaMatch($schema) - checks if $schema matches output schema of the adaptor

Tests (minimal)

• Kernel

src/Plugin/Adapter/Adapter.php

+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\experience_builder\Plugin\Adapter;
+
+use Drupal\Component\Plugin\Attribute\Plugin;
+use Drupal\Core\StringTranslation\TranslatableMarkup;
+
+/**
+ * Defines an Adapter attribute object.
+ *
+ * Plugin Namespace: Plugin\Adapter
+ *
+ * @see \Drupal\experience_builder\Plugin\Adapter\AdapterInterface
+ * @see \Drupal\experience_builder\Plugin\AdapterManager
+ * @see plugin_api
+ *
+ * @phpstan-import-type JsonSchema from \Drupal\experience_builder\SdcPropJsonSchemaType
+ */
+#[\Attribute(\Attribute::TARGET_CLASS)]
+class Adapter extends Plugin {
+
+  /**
+   * @param string $id
+   * @param \Drupal\Core\StringTranslation\TranslatableMarkup $label
+   * @param array<string, JsonSchema> $inputs
+   * @param array<string> $requiredInputs
+   * @param JsonSchema $output
+   * @param class-string|null $deriver
+   */
+  public function __construct(
+    public readonly string $id,
+    public readonly TranslatableMarkup $label,
+    protected array $inputs,
+    protected array $requiredInputs,
+    protected array $output,
+    public readonly ?string $deriver = NULL,
+  ) {}
+
+}