Issue #3502125: Add possibility of using Attributes instead of plugin annotation

Related to #3502125

src/Attribute/FapiValidationFilter.php

+<?php
+
+namespace Drupal\fapi_validation\Attribute;
+
+use Drupal\Component\Plugin\Attribute\Plugin;
+use Drupal\Core\StringTranslation\TranslatableMarkup;
+
+/**
+ * Defines a FAPI Validation Filter attribute for plugin discovery.
+ */
+#[\Attribute(\Attribute::TARGET_CLASS)]
+class FapiValidationFilter extends Plugin {
+
+  /**
+   * Constructs a FapiValidationFilter attribute.
+   *
+   * @param string $id
+   *   The plugin ID.
+   * @param \Drupal\Core\StringTranslation\TranslatableMarkup|null $label
+   *   (optional) The human-readable name of the filter type.
+   * @param \Drupal\Core\StringTranslation\TranslatableMarkup|null $description
+   *   (optional) A short description of the filter type.
+   */
+  public function __construct(
+    public readonly string $id,
+    public readonly ?TranslatableMarkup $label = NULL,
+    public readonly ?TranslatableMarkup $description = NULL,
+  ) {}
+
+}