Rework tests structure. Upgrade codeception to 2.5.3. Merge params configuration into app configuration.

api/tests/_pages/BasePage.php

@@ -0,0 +1,21 @@
+<?php
+namespace api\tests\_pages;
+
+use api\tests\FunctionalTester;
+
+class BasePage {
+
+    /**
+     * @var FunctionalTester
+     */
+    private $actor;
+
+    public function __construct(FunctionalTester $I) {
+        $this->actor = $I;
+    }
+
+    public function getActor(): FunctionalTester {
+        return $this->actor;
+    }
+
+}