Adding Custom domains (#247)

* WIP

* wip

* Finished doing most of the work

app/Http/Middleware/CustomDomainRestriction.php

@@ -0,0 +1,55 @@
+<?php
+
+namespace App\Http\Middleware;
+
+use App\Models\Forms\Form;
+use App\Models\Workspace;
+use Closure;
+use Illuminate\Http\Request;
+use Illuminate\Database\Eloquent\Builder;
+
+class CustomDomainRestriction
+{
+    const CUSTOM_DOMAIN_HEADER = "User-Custom-Domain";
+
+    /**
+     * Handle an incoming request.
+     */
+    public function handle(Request $request, Closure $next)
+    {
+        if (!$request->hasHeader(self::CUSTOM_DOMAIN_HEADER) || !config('custom-domains.enabled')) {
+            return $next($request);
+        }
+
+        $customDomain = $request->header(self::CUSTOM_DOMAIN_HEADER);
+        if (!preg_match('/^[a-z0-9]+([\-\.]{1}[a-z0-9]+)*\.[a-z]{2,5}$/', $customDomain)) {
+            return response()->json([
+                'success' => false,
+                'message' => 'Invalid domain',
+            ], 400);
+        }
+
+        // Check if domain is different from current domain
+        $notionFormsDomain = parse_url(config('app.url'))['host'];
+        if ($customDomain == $notionFormsDomain) {
+            return $next($request);
+        }
+
+        // Check if domain is known
+        if (!$workspace = Workspace::whereJsonContains('custom_domains',$customDomain)->first()) {
+            return response()->json([
+                'success' => false,
+                'message' => 'Unknown domain',
+            ], 400);
+        }
+
+        Workspace::addGlobalScope('domain-restricted', function (Builder $builder) use ($workspace) {
+            $builder->where('workspaces.id', $workspace->id);
+        });
+        Form::addGlobalScope('domain-restricted', function (Builder $builder) use ($workspace) {
+            $builder->where('forms.workspace_id', $workspace->id);
+        });
+
+        return $next($request);
+    }
+}