Add a getter to allow access to the gnutls_session_t.

[bcsgh]

Description of the Change

Add a method to yield a handle to the TLS sessions being used by libmicrohttpd for the request,

Alternate Designs

I considered building API's the provide C++ wrappers for the specific TLS API's that would be needed but concluded that is not the job of this library.

Possible Drawbacks

Verification Process

I ran a server using the new method to log data about the session.

class hello_world_resource : public httpserver::http_resource {
 public:
  const std::shared_ptr<httpserver::http_response> render(const httpserver::http_request&) override {
    auto tls = req.get_tls_session();
    LOG(INFO) << "Verion: " << gnutls_protocol_get_name(gnutls_protocol_get_version(tls));
    auto type = gnutls_certificate_type_get(tls);
    LOG(INFO) << "CertType: " << gnutls_certificate_type_get_name(type);
    unsigned int cert_count;
    auto* certs = gnutls_certificate_get_peers(tls, &cert_count);
    LOG(INFO) << "CertCount(Client): " << cert_count;
    // etc ...
  }
};

....

httpserver::webserver ws = httpserver::create_webserver(port)
            .debug()
            .log_error(+[](const std::string& err){
              std::cout << err << std::endl;
            })
            .use_ssl()
            .raw_https_mem_key(std::string{tls_server_self_signed_cert_key_pem()})
            .raw_https_mem_cert(std::string{tls_server_self_signed_cert_pem()})
            .start_method(httpserver::http::http_utils::INTERNAL_SELECT)
            .max_threads(5);

hello_world_resource hwr;
ws.register_resource("/hello", &hwr, true);
ws.start(true);

And got:

I20210517 20:59:25.343529 20745 server.cc:74] Verion: TLS1.2
I20210517 20:59:25.343542 20745 server.cc:77] CertType: X.509
I20210517 20:59:25.343555 20745 server.cc:81] CertCount(Client): 0

(This is a brand new API, with exactly 2 lines of non-declaration and no flow control. It's either works or it doesn't.)

Release Notes

Add httpserver::http_request::get_tls_session() to allow access to full TLS session.

[bcsgh]

FWIW: this reason I want this is to allow access to play around with client side cert based authentication.

[etr]

Hey, thanks for the change (and sorry for the delay on this answer). It looks good to me overall. Do you mind adding info into the documentation (the README.md) to make it discoverable? (there is a section dedicated to http_request)

[bcsgh]

Done. And while looking at it, I realized there is no easy/safe way to call that method so I added a predicate for checking that.

[etr]

Can we fix a typo in the documentation - with that done, I can merge

[etr]

Looks good, thanks for the support