Compilation warnings about hidden virtual operator overloads

[fredmorcos]

When building the PowerDNS auth, I get the following warnings coming out of yahttp.hpp.

clang --version
clang version 16.0.6
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin

In file included from ../ext/yahttp/yahttp/yahttp.hpp:19,
                 from ../pdns/webserver.hh:29,
                 from ../pdns/ws-auth.hh:29,
                 from ../pdns/ws-auth.cc:27:
../ext/yahttp/yahttp/reqresp.hpp:232:14: warning: ‘virtual YaHTTP::Request& YaHTTP::Request::operator=(const YaHTTP::HTTPBase&)’ was hidden [-Woverloaded-virtual=]
  232 |     Request& operator=(const HTTPBase& rhs) override {
      |              ^~~~~~~~
../pdns/webserver.hh:39:7: note:   by ‘HttpRequest::operator=’
   39 | class HttpRequest : public YaHTTP::Request {
      |       ^~~~~~~~~~~
../ext/yahttp/yahttp/reqresp.hpp:203:15: warning: ‘virtual YaHTTP::Response& YaHTTP::Response::operator=(const YaHTTP::HTTPBase&)’ was hidden [-Woverloaded-virtual=]
  203 |     Response& operator=(const HTTPBase& rhs) override {
      |               ^~~~~~~~
../pdns/webserver.hh:65:7: note:   by ‘HttpResponse::operator=’
   65 | class HttpResponse: public YaHTTP::Response {
      |       ^~~~~~~~~~~~