duplicate messages send fixes

http.go

@@ -38,6 +38,12 @@ func HttpPostMessage(url string, msg []byte, timeout int) (response []byte, err
 	defer resp.Body.Close()
 	body, err := io.ReadAll(resp.Body)
 	if err != nil {
+		// Server already accepted the request (2xx) — body truncation on our
+		// side doesn't mean the message wasn't stored. Return what we have so
+		// the caller doesn't retry and produce a duplicate.
+		if resp.StatusCode >= 200 && resp.StatusCode < 300 {
+			return body, nil
+		}
 		return nil, err
 	}
 	return body, nil