Add comment to explain logic in cast function.

Author: WaVEV

django_mongodb/functions.py

@@ -62,10 +62,13 @@ def cast(self, compiler, connection):
     lhs_mql = process_lhs(self, compiler, connection)[0]
     if max_length := self.output_field.max_length:
         lhs_mql = {"$substrCP": [lhs_mql, 0, max_length]}
-    if output_type == "object":
-        lhs_mql = {"$convert": {"input": lhs_mql, "to": output_type, "onError": lhs_mql}}
-    else:
+
+    # In case of "object", we skip the conversion as it doesn't need to be transformed
+    # for interpretation by JSONField. JSONField can handle various types,
+    # including int, object, or array.
+    if output_type != "object":
         lhs_mql = {"$convert": {"input": lhs_mql, "to": output_type}}
+
     if decimal_places := getattr(self.output_field, "decimal_places", None):
         lhs_mql = {"$trunc": [lhs_mql, decimal_places]}
     return lhs_mql