feat(errors): add request_id property (#769)

Author: stainless-bot

src/error.ts

@@ -13,6 +13,8 @@ export class APIError extends OpenAIError {
   readonly param: string | null | undefined;
   readonly type: string | undefined;
 
+  readonly request_id: string | null | undefined;
+
   constructor(
     status: number | undefined,
     error: Object | undefined,
@@ -22,6 +24,7 @@ export class APIError extends OpenAIError {
     super(`${APIError.makeMessage(status, error, message)}`);
     this.status = status;
     this.headers = headers;
+    this.request_id = headers?.['x-request-id'];
 
     const data = error as Record<string, any>;
     this.error = data;