Fix: detach removed users from service observers

- detach users from InventoryManagementService observers during removal
- detach users from PaymentManagementService observers during removal
- detach users from ServiceManagementService observers during removal

Fixes #1783

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/services/UserManagementService.cpp

@@ -297,6 +297,9 @@ Return type: void
 */
 void UserManagementService::removeUser(const std::string& userID)
 {
+	InventoryManagementService inventoryManagementService;
+	PaymentManagementService paymentManagementService;
+	ServiceManagementService serviceManagementService;
 	int index = m_dataStore.getUsers().find(userID);
 	if (index != -1)
 	{
@@ -304,6 +307,9 @@ void UserManagementService::removeUser(const std::string& userID)
 		if (user != nullptr)
 		{
 			user->setState(util::State::INACTIVE);
+			inventoryManagementService.detach(user);
+			paymentManagementService.detach(user);
+			serviceManagementService.detach(user);
 		}
 	}
 }