Add: allow setting your server visibility to "invite-only" (#9434)

In this mode you do register to the Game Coordinator, but your
server will not show up in the public server listing. You can give
your friends the invite code of the server with which they can
join.

src/table/settings/network_settings.ini

@@ -9,14 +9,18 @@
 [pre-amble]
 static void UpdateClientConfigValues();
 
+static std::initializer_list<const char*> _server_game_type{"local", "public", "invite-only"};
+
 static const SettingVariant _network_settings_table[] = {
 [post-amble]
 };
 [templates]
 SDTC_BOOL  =  SDTC_BOOL(              $var,        $flags, $def,                              $str, $strhelp, $strval, $pre_cb, $post_cb, $from, $to,        $cat, $extra, $startup),
+SDTC_OMANY = SDTC_OMANY(              $var, $type, $flags, $def,             $max, $full,     $str, $strhelp, $strval, $pre_cb, $post_cb, $from, $to,        $cat, $extra, $startup),
 SDTC_VAR   =   SDTC_VAR(              $var, $type, $flags, $def,       $min, $max, $interval, $str, $strhelp, $strval, $pre_cb, $post_cb, $from, $to,        $cat, $extra, $startup),
 
 [validation]
+SDTC_OMANY = static_assert($max <= MAX_$type, "Maximum value for $var exceeds storage size");
 SDTC_VAR = static_assert($max <= MAX_$type, "Maximum value for $var exceeds storage size");
 
 [defaults]
@@ -159,10 +163,16 @@ flags    = SF_NOT_IN_SAVE | SF_NO_NETWORK_SYNC | SF_NETWORK_ONLY
 def      = true
 cat      = SC_EXPERT
 
-[SDTC_BOOL]
-var      = network.server_advertise
+[SDTC_OMANY]
+var      = network.server_game_type
+type     = SLE_UINT8
 flags    = SF_NOT_IN_SAVE | SF_NO_NETWORK_SYNC | SF_NETWORK_ONLY
-def      = false
+def      = SERVER_GAME_TYPE_LOCAL
+min      = SERVER_GAME_TYPE_LOCAL
+max      = SERVER_GAME_TYPE_INVITE_ONLY
+full     = _server_game_type
+post_cb  = [](auto) { NetworkUpdateServerGameType(); }
+cat      = SC_BASIC
 
 [SDTC_BOOL]
 var      = network.autoclean_companies