Refactor services into classes (#183)

TactilityHeadless/Source/service/ServiceManifest.h

@@ -1,24 +1,22 @@
 #pragma once
 
+#include "service/Service.h"
 #include <string>
 
 namespace tt::service {
 
+// Forward declarations
 class ServiceContext;
 
-typedef void (*ServiceOnStart)(ServiceContext& service);
-typedef void (*ServiceOnStop)(ServiceContext& service);
+typedef std::shared_ptr<Service>(*CreateService)();
 
 /** A ledger that describes the main parts of a service. */
 struct ServiceManifest {
     /** The identifier by which the app is launched by the system and other apps. */
     std::string id {};
 
-    /** Non-blocking method to call when service is started. */
-    const ServiceOnStart onStart = nullptr;
-
-    /** Non-blocking method to call when service is stopped. */
-    const ServiceOnStop onStop = nullptr;
+    /** Create the instance of the app */
+    CreateService createService = nullptr;
 };
 
 } // namespace