feat: derive Deserialize, Clone, PartialEq, Eq for MetadataPrelude (#956)

Author: DiscreteTom

lambda-runtime/src/types.rs

@@ -176,7 +176,7 @@ impl<T> LambdaEvent<T> {
 }
 
 /// Metadata prelude for a stream response.
-#[derive(Debug, Default, Serialize)]
+#[derive(Debug, Default, Serialize, Deserialize, Clone, PartialEq, Eq)]
 #[serde(rename_all = "camelCase")]
 pub struct MetadataPrelude {
     #[serde(with = "http_serde::status_code")]
@@ -478,4 +478,22 @@ mod test {
 
         let _ = invoke_request_id(&headers);
     }
+
+    #[test]
+    fn serde_metadata_prelude() {
+        let metadata_prelude = MetadataPrelude {
+            status_code: StatusCode::OK,
+            headers: {
+                let mut headers = HeaderMap::new();
+                headers.insert("key", "val".parse().unwrap());
+                headers
+            },
+            cookies: vec!["cookie".to_string()],
+        };
+
+        let serialized = serde_json::to_string(&metadata_prelude).unwrap();
+        let deserialized: MetadataPrelude = serde_json::from_str(&serialized).unwrap();
+
+        assert_eq!(metadata_prelude, deserialized);
+    }
 }