Create the systems.cpp for the boss fight mini game.

boss/system.cpp

@@ -0,0 +1,29 @@
+#include "boss/system.hpp"
+#include <fmt/core.h>
+#include "components.hpp"
+#include "game_level.hpp"
+
+namespace boss {
+  using namespace components;
+
+  void System::load_config() {
+    fmt::println("load it");
+  }
+
+  shared_ptr<boss::UI> System::create_bossfight() {
+    auto& level = GameDB::current_level();
+    auto prev_world = GameDB::current_world();
+    dbc::check(prev_world != nullptr, "Starter world for boss fights can't be null.");
+    auto world = GameDB::clone_load_world(prev_world);
+    auto& config = prev_world->get_the<GameConfig>();
+
+    auto boss_names = config.bosses.keys();
+    auto& level_name = boss_names[level.index % boss_names.size()];
+    auto& boss_data = config.bosses[level_name];
+
+    auto boss_id = world->entity();
+    components::configure_entity(*world, boss_id, boss_data["components"]);
+
+    return make_shared<boss::UI>(world, boss_id);
+  }
+}