fix: preserve cookie masking on malformed unicode

Signed-off-by: lucarlig <luca.carlig@ibm.com>

Author: lucarlig

tests/performance/test_request_logging_masking_sidecar_benchmark.py

@@ -154,6 +154,7 @@ def rust_headers(payload: Any) -> Any:
         [
             {"Authorization": "Bearer abc", "Cookie": "jwt_token=abc; theme=dark", "X-Trace-Id": "123"},
             {"X-Auth-Count": "5", "X-Api-Key": "secret"},
+            {"Cookie": "jwt_token=\ud800; theme=dark"},
         ],
     )
 

tools_rust/request_logging_masking_sidecar/src/lib.rs

@@ -218,8 +218,8 @@ fn mask_sensitive_headers(py: Python<'_>, headers: &Bound<'_, PyAny>) -> PyResul
         }
 
         if key_text.eq_ignore_ascii_case("cookie") && value.is_instance_of::<PyString>() {
-            let cookie_value = value.cast::<PyString>()?.to_str()?;
-            masked.set_item(key, mask_cookie_header(cookie_value))?;
+            let cookie_value = value.cast::<PyString>()?.to_string_lossy();
+            masked.set_item(key, mask_cookie_header(cookie_value.as_ref()))?;
             continue;
         }