feat: Phase 4 - Mailwizz integration with subscriber sync and retry

app/Services/DispatchUnsyncedMailwizzSyncJobsService.php

@@ -0,0 +1,46 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Services;
+
+use App\Jobs\SyncSubscriberToMailwizz;
+use App\Models\Subscriber;
+use Illuminate\Database\Eloquent\Builder;
+
+final class DispatchUnsyncedMailwizzSyncJobsService
+{
+    /**
+     * Dispatch a Mailwizz sync job for each subscriber that is not synced yet and whose page has Mailwizz configured.
+     * Duplicate jobs for the same subscriber are skipped while a job is already pending or running (unique lock on SyncSubscriberToMailwizz).
+     *
+     * @return int Number of eligible subscribers (dispatch was attempted for each; some attempts may be skipped as duplicates)
+     */
+    public function dispatch(?int $preregistrationPageId = null): int
+    {
+        $query = $this->eligibleSubscribersQuery();
+        if ($preregistrationPageId !== null) {
+            $query->where('preregistration_page_id', $preregistrationPageId);
+        }
+
+        $count = 0;
+        $query->chunkById(200, function ($subscribers) use (&$count): void {
+            foreach ($subscribers as $subscriber) {
+                SyncSubscriberToMailwizz::dispatch($subscriber);
+                $count++;
+            }
+        });
+
+        return $count;
+    }
+
+    /**
+     * @return Builder<Subscriber>
+     */
+    public function eligibleSubscribersQuery(): Builder
+    {
+        return Subscriber::query()
+            ->where('synced_to_mailwizz', false)
+            ->whereHas('preregistrationPage.mailwizzConfig');
+    }
+}