stub add

src/HeartTrackAPI/AppBootstrap.cs

@@ -72,6 +72,8 @@ public class AppBootstrap(IConfiguration configuration)
                     services.AddDbContext<HeartTrackContext>(options =>
                         options.UseSqlite(connectionString), ServiceLifetime.Singleton);
                 }
+                services.AddSingleton<IDataManager>(provider => new DbDataManager(provider.GetService<HeartTrackContext>()));
+
                 break;
                 
         }