Implemented WebHooks delivery queue.

Completely removed usage of the RabbitMQ. Queue now based on Redis channels.
Worker process now extracted as separate docker container.
Base image upgraded to the 1.8.0 version (PHP 7.2.7 and pcntl extension).

common/tasks/PullMojangUsername.php

@@ -0,0 +1,72 @@
+<?php
+declare(strict_types=1);
+
+namespace common\tasks;
+
+use api\exceptions\ThisShouldNotHappenException;
+use common\components\Mojang\Api as MojangApi;
+use common\components\Mojang\exceptions\MojangApiException;
+use common\components\Mojang\exceptions\NoContentException;
+use common\models\Account;
+use common\models\MojangUsername;
+use GuzzleHttp\Exception\RequestException;
+use Yii;
+use yii\queue\JobInterface;
+
+class PullMojangUsername implements JobInterface {
+
+    public $username;
+
+    public static function createFromAccount(Account $account): self {
+        $result = new static();
+        $result->username = $account->username;
+
+        return $result;
+    }
+
+    /**
+     * @param \yii\queue\Queue $queue which pushed and is handling the job
+     *
+     * @throws \Exception
+     */
+    public function execute($queue) {
+        Yii::$app->statsd->inc('queue.pullMojangUsername.attempt');
+        $mojangApi = $this->createMojangApi();
+        try {
+            $response = $mojangApi->usernameToUUID($this->username);
+            Yii::$app->statsd->inc('queue.pullMojangUsername.found');
+        } catch (NoContentException $e) {
+            $response = false;
+            Yii::$app->statsd->inc('queue.pullMojangUsername.not_found');
+        } catch (RequestException | MojangApiException $e) {
+            Yii::$app->statsd->inc('queue.pullMojangUsername.error');
+            return;
+        }
+
+        /** @var MojangUsername|null $mojangUsername */
+        $mojangUsername = MojangUsername::findOne($this->username);
+        if ($response === false) {
+            if ($mojangUsername !== null) {
+                $mojangUsername->delete();
+            }
+        } else {
+            if ($mojangUsername === null) {
+                $mojangUsername = new MojangUsername();
+                $mojangUsername->username = $response->name;
+                $mojangUsername->uuid = $response->id;
+            } else {
+                $mojangUsername->uuid = $response->id;
+                $mojangUsername->touch('last_pulled_at');
+            }
+
+            if (!$mojangUsername->save()) {
+                throw new ThisShouldNotHappenException('Cannot save mojang username');
+            }
+        }
+    }
+
+    protected function createMojangApi(): MojangApi {
+        return new MojangApi();
+    }
+
+}