Add "level" to PartCategory serializer

- Also use tree ordering by default

InvenTree/part/api.py

@@ -118,9 +118,17 @@ class CategoryList(generics.ListCreateAPIView):
 
     ordering_fields = [
         'name',
+        'level',
+        'tree_id',
+        'lft',
     ]
 
-    ordering = 'name'
+    # Use hierarchical ordering by default
+    ordering = [
+        'tree_id',
+        'lft',
+        'name'
+    ]
 
     search_fields = [
         'name',

InvenTree/part/serializers.py

@@ -32,6 +32,8 @@ class CategorySerializer(InvenTreeModelSerializer):
 
     parts = serializers.IntegerField(source='item_count', read_only=True)
 
+    level = serializers.IntegerField(read_only=True)
+
     class Meta:
         model = PartCategory
         fields = [
@@ -40,10 +42,11 @@ class CategorySerializer(InvenTreeModelSerializer):
             'description',
             'default_location',
             'default_keywords',
-            'pathstring',
-            'url',
+            'level',
             'parent',
             'parts',
+            'pathstring',
+            'url',
         ]