Extract automation API to MailPoet REST API

[MAILPOET-4523]

mailpoet/lib/API/REST/Endpoint.php

@@ -0,0 +1,18 @@
+<?php declare(strict_types = 1);
+
+namespace MailPoet\API\REST;
+
+use MailPoet\Validator\Schema;
+
+abstract class Endpoint {
+  abstract public function handle(Request $request): Response;
+
+  public function checkPermissions(): bool {
+    return current_user_can('admin');
+  }
+
+  /** @return array<string, Schema> */
+  public static function getRequestSchema(): array {
+    return [];
+  }
+}