load jira custom_fields as json (#14494)

Author: paulOsinski

dojo/api_v2/serializers.py

@@ -1428,6 +1428,12 @@ def validate(self, data):
             msg = "Either engagement or product has to be set."
             raise serializers.ValidationError(msg)
 
+        if "custom_fields" in data and isinstance(data["custom_fields"], str):
+            try:
+                data["custom_fields"] = json.loads(data["custom_fields"])
+            except json.JSONDecodeError as e:
+                raise serializers.ValidationError({"custom_fields": f"Invalid JSON: {e}"}) from e
+
         return data