Closes #1196: Added a lag_id filter to the API interfaces view

netbox/dcim/filters.py

@@ -477,6 +477,11 @@ class InterfaceFilter(DeviceComponentFilterSet):
         method='filter_type',
         label='Interface type',
     )
+    lag_id = django_filters.ModelMultipleChoiceFilter(
+        name='lag',
+        queryset=Interface.objects.all(),
+        label='LAG interface (ID)',
+    )
     mac_address = django_filters.CharFilter(
         method='_mac_address',
         label='MAC address',