add appsettings serializers and docs

backend/common/serializers.py

@@ -5,6 +5,26 @@
 from rest_framework import serializers
 
 
+class ValidateUnknownFieldsMixin:
+    """
+    Mixin to validate and reject unknown fields in a serializer.
+    """
+
+    def to_internal_value(self, data):
+        """check expected keys"""
+        allowed_fields = set(self.fields.keys())
+        input_fields = set(data.keys())
+
+        # Find unknown fields
+        unknown_fields = input_fields - allowed_fields
+        if unknown_fields:
+            raise serializers.ValidationError(
+                {"error": f"Unknown fields: {', '.join(unknown_fields)}"}
+            )
+
+        return super().to_internal_value(data)
+
+
 class ErrorResponseSerializer(serializers.Serializer):
     """error message"""
 
@@ -27,3 +47,11 @@ class PaginationSerializer(serializers.Serializer):
         child=serializers.IntegerField(), allow_null=True
     )
     total_hits = serializers.IntegerField()
+
+
+class AsyncTaskResponseSerializer(serializers.Serializer):
+    """serialize new async task"""
+
+    message = serializers.CharField()
+    task_id = serializers.CharField()
+    filename = serializers.CharField(required=False)