Empty password leads to an authorization error, which isn't ideal.
Also log the response in case its an error, I think this would be handy
in case the upstream starts misbehaving. By default won't add to log
noise.
Example:
```
curl -s -u ':' -d "test" ntfy.sh/test | jq .
{
"code": 40101,
"http": 401,
"error": "unauthorized",
"link": "https://ntfy.sh/docs/publish/#authentication"
}
```
