fix: turn headers serializer into a deserializer (#502)

* serializer into deserializer

* update deserializer usages

Author: duncanista

bottlecap/src/lifecycle/invocation/triggers/api_gateway_http_event.rs

@@ -16,7 +16,7 @@ use crate::lifecycle::invocation::{
 pub struct APIGatewayHttpEvent {
     #[serde(rename = "routeKey")]
     pub route_key: String,
-    #[serde(serialize_with = "lowercase_key")]
+    #[serde(deserialize_with = "lowercase_key")]
     pub headers: HashMap<String, String>,
     #[serde(rename = "requestContext")]
     pub request_context: RequestContext,

bottlecap/src/lifecycle/invocation/triggers/api_gateway_rest_event.rs

@@ -14,7 +14,7 @@ use crate::lifecycle::invocation::{
 
 #[derive(Debug, Serialize, Deserialize, Clone, PartialEq)]
 pub struct APIGatewayRestEvent {
-    #[serde(serialize_with = "lowercase_key")]
+    #[serde(deserialize_with = "lowercase_key")]
     pub headers: HashMap<String, String>,
     #[serde(rename = "requestContext")]
     pub request_context: RequestContext,
@@ -205,8 +205,8 @@ mod tests {
 
         let expected = APIGatewayRestEvent {
             headers: HashMap::from([
-                ("Header1".to_string(), "value1".to_string()),
-                ("Header2".to_string(), "value2".to_string()),
+                ("header1".to_string(), "value1".to_string()),
+                ("header2".to_string(), "value2".to_string()),
             ]),
             request_context: RequestContext {
                 stage: "$default".to_string(),

bottlecap/src/lifecycle/invocation/triggers/lambda_function_url_event.rs

@@ -11,7 +11,7 @@ use crate::lifecycle::invocation::{
 
 #[derive(Debug, Serialize, Deserialize, Clone, PartialEq)]
 pub struct LambdaFunctionUrlEvent {
-    #[serde(serialize_with = "lowercase_key")]
+    #[serde(deserialize_with = "lowercase_key")]
     pub headers: HashMap<String, String>,
     #[serde(rename = "requestContext")]
     pub request_context: RequestContext,

bottlecap/src/lifecycle/invocation/triggers/mod.rs

@@ -1,7 +1,7 @@
-use std::{collections::HashMap, hash::BuildHasher};
+use std::collections::HashMap;
 
 use datadog_trace_protobuf::pb::Span;
-use serde::{ser::SerializeMap, Serializer};
+use serde::{Deserialize, Deserializer};
 use serde_json::Value;
 
 pub mod api_gateway_http_event;
@@ -68,19 +68,16 @@ pub fn get_aws_partition_by_region(region: &str) -> String {
 
 /// Serialize a `HashMap` with lowercase keys
 ///
-pub fn lowercase_key<S, H>(
-    map: &HashMap<String, String, H>,
-    serializer: S,
-) -> Result<S::Ok, S::Error>
+pub fn lowercase_key<'de, D, V>(deserializer: D) -> Result<HashMap<String, V>, D::Error>
 where
-    S: Serializer,
-    H: BuildHasher,
+    D: Deserializer<'de>,
+    V: Deserialize<'de>,
 {
-    let mut map_serializer = serializer.serialize_map(Some(map.len()))?;
-    for (key, value) in map {
-        map_serializer.serialize_entry(&key.to_lowercase(), value)?;
-    }
-    map_serializer.end()
+    let map = HashMap::<String, V>::deserialize(deserializer)?;
+    Ok(map
+        .into_iter()
+        .map(|(key, value)| (key.to_lowercase(), value))
+        .collect())
 }
 
 #[cfg(test)]

bottlecap/tests/payloads/api_gateway_http_event.json

@@ -4,17 +4,17 @@
     "rawPath": "/httpapi/get",
     "rawQueryString": "",
     "headers": {
-        "accept": "*/*",
-        "content-length": "0",
-        "host": "x02yirxc7a.execute-api.sa-east-1.amazonaws.com",
-        "user-agent": "curl/7.64.1",
-        "x-amzn-trace-id": "Root=1-613a52fb-4c43cfc95e0241c1471bfa05",
-        "x-forwarded-for": "38.122.226.210",
-        "x-forwarded-port": "443",
-        "x-forwarded-proto": "https",
-        "x-datadog-trace-id": "12345",
-        "x-datadog-parent-id": "67890",
-        "x-datadog-sampling-priority": "2"
+        "Accept": "*/*",
+        "Content-Length": "0",
+        "Host": "x02yirxc7a.execute-api.sa-east-1.amazonaws.com",
+        "User-Agent": "curl/7.64.1",
+        "X-amzn-trace-id": "Root=1-613a52fb-4c43cfc95e0241c1471bfa05",
+        "X-forwarded-for": "38.122.226.210",
+        "X-forwarded-port": "443",
+        "X-forwarded-proto": "https",
+        "X-datadog-trace-id": "12345",
+        "X-datadog-parent-id": "67890",
+        "X-datadog-sampling-priority": "2"
     },
     "requestContext": {
         "accountId": "425362996713",