feat: add Response_code.is_success

src/Tiny_httpd_server.ml

@@ -42,6 +42,8 @@ module Response_code = struct
     | 501 -> "Not implemented"
     | 503 -> "Service unavailable"
     | n -> "Unknown response code " ^ string_of_int n (* TODO *)
+
+  let[@inline] is_success n = n >= 200 && n < 400
 end
 
 type 'a resp_result = ('a, Response_code.t * string) result

src/Tiny_httpd_server.mli

@@ -195,6 +195,10 @@ module Response_code : sig
   val descr : t -> string
   (** A description of some of the error codes.
       NOTE: this is not complete (yet). *)
+
+  val is_success : t -> bool
+  (** [is_success code] is true iff [code] is in the [2xx] or [3xx] range.
+      @since NEXT_RELEASE *)
 end
 
 (** {2 Responses}