Join, leave, registrations endpoints

todo: remove smb from event endpoint

WebApp/Program.cs

@@ -53,5 +53,6 @@ app.UseRouting(); // Enables routing to match incoming request to endpoints
 app.MapEventsEndpoints();
 app.MapOrganizationsEndpoints();
 app.MapAuthEndpoints();
+app.MapEventsRegistrationEndpoints();
 
 app.Run();