1. Successfully built using Docker.
2. Successfully call the function from C++:
```
#include "cxxbridge_code/src/lib.rs.h"
#include "rust/cxx.h
...
const std::string server_key = argv[1];
const std::string device_token = argv[2];
const std::string message_title = argv[3];
const std::string message_body = argv[4];
sendNotifToFCM(server_key, device_token, message_title, message_body);
```