:sig
bool server_stop(String key)

:params
key : runtime-wide server key used with `server_start_http()`
return value : `true` when no listener remains or a stop signal was sent

:see
>sys
server_start_http

:content
Stops a custom server listener by key and removes its registry config.

`server_stop()` currently targets custom servers started through `server_start_http()`. The same key model is intended to extend to future `server_start_tcp()` and `server_start_udp()` helpers.

:example
server_start_http("doc-demo-stop", "/tmp/uce/custom-servers/doc-stop.sock", "examples/sample_unit.uce", "RENDER");
print(server_stop("doc-demo-stop") ? "server stopped" : "no such server", "\n");