Add endpoint-class factory based on PSR-11 container interface

[MAILPOET-4135]

mailpoet/lib/Automation/API/EndpointFactory.php

@@ -0,0 +1,25 @@
+<?php declare(strict_types = 1);
+
+namespace MailPoet\Automation\API;
+
+use MailPoet\InvalidStateException;
+use MailPoetVendor\Psr\Container\ContainerInterface;
+
+class EndpointFactory {
+  /** @var ContainerInterface */
+  private $container;
+
+  public function __construct(
+    ContainerInterface $container
+  ) {
+    $this->container = $container;
+  }
+
+  public function createEndpoint(string $class): Endpoint {
+    $endpoint = $this->container->get($class);
+    if (!$endpoint instanceof Endpoint) {
+      throw new InvalidStateException(sprintf("Class '%s' doesn't implement '%s'", $class, Endpoint::class));
+    }
+    return $endpoint;
+  }
+}