Changes with nginx 1.19.0 26 May 2020
*) Feature: client certificate validation with OCSP.
*) Bugfix: "upstream sent frame for closed stream" errors might occur when working with gRPC backends.
*) Bugfix: OCSP stapling might not work if the "resolver" directive was not specified.
*) Bugfix: connections with incorrect HTTP/2 preface were not logged.