feat(catalog,contacts): fresh catalog and contacts implementation

app/Domains/Catalog/Http/Resources/UnitResource.php

@@ -0,0 +1,36 @@
+<?php
+
+namespace App\Domains\Catalog\Http\Resources;
+
+use App\Domains\Accounts\Http\Resources\CompanyResource;
+use Illuminate\Http\Request;
+use Illuminate\Http\Resources\Json\JsonResource;
+
+/**
+ * The payload for a measurement unit: its identity plus the company it
+ * belongs to.
+ *
+ * The owning company is expanded only when the relation resolves, so the
+ * `company` key is absent -- not null -- for a unit whose company row is
+ * missing. Checking that costs an existence query per serialised unit.
+ */
+class UnitResource extends JsonResource
+{
+    /**
+     * Transform the resource into an array.
+     *
+     * @param  Request  $request
+     */
+    public function toArray($request): array
+    {
+        return [
+            'id' => $this->id,
+            'name' => $this->name,
+            'company_id' => $this->company_id,
+            'company' => $this->when(
+                $this->company()->exists(),
+                fn () => new CompanyResource($this->company)
+            ),
+        ];
+    }
+}