add hostname to config

src/app.ml

@@ -42,6 +42,14 @@ let open_registration =
 
 let () = Dream.log "open_registration: %b" open_registration
 
+let hostname =
+  match Scfg.Query.get_dir "hostname" config with
+  | None -> failwith "no `hostname` in configuration file"
+  | Some hostname ->
+    Result.fold ~error:failwith ~ok:Fun.id (Scfg.Query.get_param 0 hostname)
+
+let () = Dream.log "hostname: %s" hostname
+
 let port =
   match Scfg.Query.get_dir "port" config with
   | None -> 8080