fix: serialize AlbTargetGroupRequest::query_string_parameters value to string

fix awslabs#954

Author: DiscreteTom

lambda-events/src/event/alb/mod.rs

@@ -17,6 +17,7 @@ pub struct AlbTargetGroupRequest {
     #[serde(default)]
     pub path: Option<String>,
     #[serde(default)]
+    #[serde(serialize_with = "query_map::serde::aws_api_gateway_v1::serialize_query_string_parameters")]
     pub query_string_parameters: QueryMap,
     #[serde(default)]
     pub multi_value_query_string_parameters: QueryMap,
@@ -70,6 +71,7 @@ pub struct AlbTargetGroupResponse {
 #[cfg(test)]
 mod test {
     use super::*;
+    use serde_json::Value;
 
     #[test]
     #[cfg(feature = "alb")]
@@ -91,6 +93,19 @@ mod test {
         assert_eq!(parsed, reparsed);
     }
 
+    #[test]
+    #[cfg(feature = "alb")]
+    fn ensure_alb_lambda_target_request_query_string_parameter_value_is_string() {
+        let data = include_bytes!("../../fixtures/example-alb-lambda-target-request-headers-only.json");
+        let parsed: AlbTargetGroupRequest = serde_json::from_slice(data).unwrap();
+        let output: String = serde_json::to_string(&parsed).unwrap();
+        let reparsed: Value = serde_json::from_slice(output.as_bytes()).unwrap();
+        assert_eq!(
+            reparsed["queryStringParameters"]["key"],
+            Value::String("hello".to_string())
+        );
+    }
+
     #[test]
     #[cfg(feature = "alb")]
     fn example_alb_lambda_target_response() {