Add option to configure auto discovery(mDNS)

resolves #539
potentially resolves #611

src/config.cpp

@@ -580,6 +580,7 @@ namespace config {
   sunshine_t sunshine {
     false, // hide_tray_controls
     true, // enable_pairing
+    true, // enable_discovery
     "en",  // locale
     2,  // min_log_level
     0,  // flags
@@ -1280,6 +1281,7 @@ namespace config {
 
     bool_f(vars, "hide_tray_controls", sunshine.hide_tray_controls);
     bool_f(vars, "enable_pairing", sunshine.enable_pairing);
+    bool_f(vars, "enable_discovery", sunshine.enable_discovery);
     bool_f(vars, "notify_pre_releases", sunshine.notify_pre_releases);
 
     int port = sunshine.port;

src/config.h

@@ -254,6 +254,7 @@ namespace config {
   struct sunshine_t {
     bool hide_tray_controls;
     bool enable_pairing;
+    bool enable_discovery;
     std::string locale;
     int min_log_level;
     std::bitset<flag::FLAG_SIZE> flags;

src/main.cpp

@@ -325,7 +325,9 @@ int main(int argc, char *argv[]) {
 
   std::unique_ptr<platf::deinit_t> mDNS;
   auto sync_mDNS = std::async(std::launch::async, [&mDNS]() {
-    mDNS = platf::publish::start();
+    if (config::sunshine.enable_discovery) {
+      mDNS = platf::publish::start();
+    }
   });
 
   std::unique_ptr<platf::deinit_t> upnp_unmap;