Review, publish, preview and undo changes through the API

Revisions now call publishing only what publishes: a project's status is
whether the work is active, and a service is published by its flag.

The fake identity server answers by token, so a test can sign in a second
person.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app/Http/Controllers/Api/V1/Concerns/ResolvesContent.php

@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Http\Controllers\Api\V1\Concerns;
+
+use App\Support\AdminContent;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Http\Request;
+
+/**
+ * For the endpoints shared by several kinds of content —
+ * `/pages/{page}/revisions`, `/projects/{project}/revisions` — whose route
+ * says which kind through its `content` default.
+ */
+trait ResolvesContent
+{
+    protected function content(Request $request): string
+    {
+        return (string) $request->route('content');
+    }
+
+    protected function record(Request $request): Model
+    {
+        $content = $this->content($request);
+
+        return AdminContent::find($content, $request->route(AdminContent::parameter($content)));
+    }
+}