[Web][Tests] Add PHPUnit setup and imapsync module tests

tests/php/Support/FakeOAuthClient.php

@@ -0,0 +1,35 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Mailcow\Tests\Support;
+
+use Mailcow\Imapsync\Http\OAuthClient;
+
+/**
+ * OAuthClient without network: resolve() answers from $addresses, send() records the curl options
+ * and returns $response.
+ */
+class FakeOAuthClient extends OAuthClient
+{
+    /** @var array<string, string[]> host => addresses */
+    public array $addresses = [];
+    /** @var array{0: string|false, 1: int} */
+    public array $response = ['{}', 200];
+    /** @var array[] curl options of every send() */
+    public array $sent = [];
+    /** @var string[] hosts passed to resolve() */
+    public array $resolved = [];
+
+    protected function resolve(string $host): array
+    {
+        $this->resolved[] = $host;
+        return $this->addresses[$host] ?? [];
+    }
+
+    protected function send(array $options): array
+    {
+        $this->sent[] = $options;
+        return $this->response;
+    }
+}