Add deepMerge method for enhanced property merging

Introduce a deepMerge method to handle nested property merges more effectively. This addition includes updates to the Response, MergesProps, and ResponseFactory classes, enabling nested properties to be merged and tracked separately.

src/Inertia.php

@@ -18,6 +18,7 @@
  * @method static \Inertia\DeferProp defer(callable $callback, string $group = 'default')
  * @method static \Inertia\AlwaysProp always(mixed $value)
  * @method static \Inertia\MergeProp merge(mixed $value)
+ * @method static \Inertia\MergeProp deepMerge(mixed $value)
  * @method static \Inertia\Response render(string $component, array|\Illuminate\Contracts\Support\Arrayable $props = [])
  * @method static \Symfony\Component\HttpFoundation\Response location(string|\Symfony\Component\HttpFoundation\RedirectResponse $url)
  * @method static void macro(string $name, object|callable $macro)

src/MergesProps.php

@@ -6,6 +6,8 @@ trait MergesProps
 {
     protected bool $merge = false;
 
+    protected bool $deepMerge = false;
+
     public function merge(): static
     {
         $this->merge = true;
@@ -17,4 +19,16 @@ public function shouldMerge(): bool
     {
         return $this->merge;
     }
+
+    public function deepMerge(): static
+    {
+        $this->deepMerge = true;
+
+        return $this;
+    }
+
+    public function shouldDeepMerge(): bool
+    {
+        return $this->deepMerge;
+    }
 }

src/Response.php

@@ -293,7 +293,18 @@ public function resolveMergeProps(Request $request): array
         $mergeProps = collect($this->props)
             ->filter(function ($prop) {
                 return $prop instanceof Mergeable;
+            });
+
+        $deepMergeProps = $mergeProps
+            ->filter(function ($prop) {
+                return $prop->shouldDeepMerge();
+            })
+            ->filter(function ($prop, $key) use ($resetProps) {
+                return ! $resetProps->contains($key);
             })
+            ->keys();
+
+        $mergeProps = $mergeProps
             ->filter(function ($prop) {
                 return $prop->shouldMerge();
             })
@@ -302,7 +313,10 @@ public function resolveMergeProps(Request $request): array
             })
             ->keys();
 
-        return $mergeProps->isNotEmpty() ? ['mergeProps' => $mergeProps->toArray()] : [];
+        return $mergeProps->isNotEmpty() ? [
+            'mergeProps' => $mergeProps->toArray(),
+            'deepMergeProps' => $deepMergeProps->toArray()
+        ] : [];
     }
 
     public function resolveDeferredProps(Request $request): array

src/ResponseFactory.php

@@ -122,6 +122,14 @@ public function merge($value): MergeProp
         return new MergeProp($value);
     }
 
+    /**
+     * @param  mixed  $value
+     */
+    public function deepMerge($value): MergeProp
+    {
+        return (new MergeProp($value))->deepMerge();
+    }
+
     /**
      * @param  mixed  $value
      */