Should http.status_code be an Integer, not a String?

[blandflakes]

Hello, we're using natchez for tracing, very pleased.

We're trying to bump to 0.0.22, but our HTTP4s services start failing requests due to a ClassCastException.

I did some digging, and I found the cause. Recent versions of dd-trace have started looking at the http.status_code flag, which is expected to be an Integer, not a String:

DataDog/dd-trace-java@e6a2a36#diff-9df24c921979abf616256e047e43b08aa0ad40ef7ac721632512765ec47e1b9cL103

This only recently started breaking because the status code was hardcoded to 0 before; they weren't examining the tag.

The documentation for natchez-https perhaps hints that the String type is surprising, if I'm interpreting "String (!)" correctly.

Is there a reason it's a String, or would you be open to moving it to an Int? I'm happy to contribute with a PR if that's something you'd like.