asset: make HandleUntyped<T>::id private

crates/bevy_asset/src/handle.rs

@@ -322,8 +322,7 @@ impl<T: Asset> Clone for Handle<T> {
 /// To convert back to a typed handle, use the [typed](HandleUntyped::typed) method.
 #[derive(Debug)]
 pub struct HandleUntyped {
-    /// An unique identifier to an Asset.
-    pub id: HandleId,
+    id: HandleId,
     handle_type: HandleType,
 }
 
@@ -352,6 +351,12 @@ impl HandleUntyped {
         }
     }
 
+    /// The ID of the asset.
+    #[inline]
+    pub fn id(&self) -> HandleId {
+        self.id
+    }
+
     /// Creates a weak copy of this handle.
     #[must_use]
     pub fn clone_weak(&self) -> Self {