No convenient way to send a custom error message

[edgar-bonet]

Prior to commit e557721, it was easy to send a custom error message to the client:

conn->error(conn, HTTP_STATUS_BAD_REQUEST, "I cannot understand this POST data.\n");

would give:

$ curl localhost:8000 -d zborglh
I cannot understand this POST data.

Since that commit, the error() method is no longer available. Instead, we have a new method called send_error(), which always sends an empty body:

conn->send_error(conn, HTTP_STATUS_BAD_REQUEST, "I cannot understand this POST data.");

gives:

$ curl localhost:8000 -d zborglh
$     # ← empty response body

Inspecting the full response, it appears the custom message is sent, but it is sent as the status text:

$ curl -i localhost:8000 -d zborglh
HTTP/1.1 400 I cannot understand this POST data.
Server: Libuhttpd/3.14.1
Content-Length: 0
Content-Type: text/plain
Connection: close

A custom status text is far less useful than a custom message within the response body. Would you please consider restoring the functionality of the previous error() method?