Accept text/plain events from the Plausible tracker

The Plausible tracker posts its JSON payload with Content-Type text/plain,
  which Laravel does not parse, so every real event failed validation and
  was redirected instead of being forwarded.

  - Decode the raw body when the request is not JSON
  - Respond with 400 instead of a redirect on invalid non-JSON requests
  - Trim trailing slash from the configured domain when forwarding events
  - Add a 5s timeout and respond with 502 when Plausible is unreachable

src/Http/Controllers/PlausibleEventApiController.php

@@ -2,18 +2,30 @@
 
 namespace Mattitja\LaravelPlausibleProxy\Http\Controllers;
 
+use Illuminate\Http\Client\ConnectionException;
 use Illuminate\Http\Response;
 use Illuminate\Support\Facades\Http;
+use Illuminate\Support\Facades\Log;
 use Mattitja\LaravelPlausibleProxy\Http\Requests\PlausibleEventRequest;
 
 class PlausibleEventApiController
 {
     public function __invoke(PlausibleEventRequest $request): Response
     {
-        $upstream = Http::withHeaders([
-            'User-Agent' => (string) $request->userAgent(),
-            'X-Forwarded-For' => (string) $request->ip(),
-        ])->post(config('plausible-proxy.domain').'/api/event', $request->all());
+        $url = rtrim((string) config('plausible-proxy.domain'), '/').'/api/event';
+
+        try {
+            $upstream = Http::timeout(5)
+                ->withHeaders([
+                    'User-Agent' => (string) $request->userAgent(),
+                    'X-Forwarded-For' => (string) $request->ip(),
+                ])
+                ->post($url, $request->all());
+        } catch (ConnectionException $e) {
+            Log::error('Failed to forward Plausible event: '.$e->getMessage());
+
+            return response('Bad Gateway', 502);
+        }
 
         return response($upstream->body(), $upstream->status())
             ->header('Content-Type', $upstream->header('Content-Type') ?: 'text/plain');