Add support for matchmaker sending clients off to game server

rc_core/src/persist/config/cubes_json.rs

@@ -353,4 +353,16 @@ impl <C: Clone + Send> super::ConfigProvider<C> for CubeConfig {
             items: id_map,
         })
     }*/
+
+    fn players_per_game(&self) -> usize {
+        self.battle.multiplayer.players_per_game
+    }
+
+    fn is_multiplayer_enabled(&self) -> bool {
+        self.battle.multiplayer.enabled
+    }
+
+    fn network_config(&self) -> crate::persist::NetworkConf {
+        self.battle.multiplayer.network.clone()
+    }
 }

rc_core/src/persist/config/traits.rs

@@ -25,8 +25,11 @@ pub trait ConfigProvider<C: Clone> {
     fn cubes(&self) -> &'_ std::collections::HashMap<String, crate::persist::Cube>;
     fn chat_system_config(&self) -> ChatSystemConfig;
     fn gamemode_events(&self) -> GameEventSequence;
-    // FIXME don't use serializable types in traits
     fn singleplayer_details(&self) -> SingleplayerConfig;
+    fn players_per_game(&self) -> usize;
+    fn is_multiplayer_enabled(&self) -> bool;
+    // FIXME don't use serializable types in traits
+    fn network_config(&self) -> crate::persist::NetworkConf;
 }
 
 pub struct CompleteCampaignProvider {