Extract Responses header conversion into a shared module (#48200)

Move JSON-to-HTTP header conversion from `responses_websocket` into the
crate-wide `responses_headers` module and update the WebSocket code to use it.
Preserve conversion of string, number, and boolean values, while continuing to
ignore invalid header names and unsupported or invalid values.

GitOrigin-RevId: f179de214cf763549b5b8a898dc4bcda3ce07ebd

codex-rs/codex-api/src/responses_headers.rs

@@ -0,0 +1,32 @@
+//! Converts headers in Responses event payloads to HTTP headers.
+//! Invalid names and unsupported or invalid values are ignored.
+
+use http::HeaderMap;
+use http::HeaderName;
+use http::HeaderValue;
+use serde_json::Value;
+use serde_json::map::Map as JsonMap;
+
+pub(crate) fn json_headers_to_http_headers(headers: &JsonMap<String, Value>) -> HeaderMap {
+    let mut mapped = HeaderMap::new();
+    for (name, value) in headers {
+        let Ok(header_name) = HeaderName::from_bytes(name.as_bytes()) else {
+            continue;
+        };
+        let Some(header_value) = json_header_value(value) else {
+            continue;
+        };
+        mapped.insert(header_name, header_value);
+    }
+    mapped
+}
+
+fn json_header_value(value: &Value) -> Option<HeaderValue> {
+    let value = match value {
+        Value::String(value) => value.clone(),
+        Value::Number(value) => value.to_string(),
+        Value::Bool(value) => value.to_string(),
+        _ => return None,
+    };
+    HeaderValue::from_str(&value).ok()
+}