requestId property Null safety
You can specify an optional unique request ID, and if you need to retry your request, the server will know to ignore the request if it's complete.
For example, you make an initial request and the request times out. If you
make the request again with the same request ID, the server can check if
it received the original operation with the same request ID. If it did, it
will ignore the second request. The request ID must be a valid
UUID with the exception that zero
UUID is not supported (