public async Task <ServiceResponse <List <GetRegistrationDTO> > > AddRegistration(AddRegistrationDTO newRegistration)
        {
            ServiceResponse <List <GetRegistrationDTO> > serviceResponse = new ServiceResponse <List <GetRegistrationDTO> >();

            Registration registration = _mapper.Map <Registration>(newRegistration);

            // Associating new registration with user's JWT claim "u => u.Id == GetUserId()"
            registration.User = await _context.Users.FirstOrDefaultAsync(u => u.Id == GetUserId());

            await _context.Registrations.AddAsync(registration);

            await _context.SaveChangesAsync();

            serviceResponse.Data    = (_context.Registrations.Select(c => _mapper.Map <GetRegistrationDTO>(c))).ToList();
            serviceResponse.Message = "User has succesfully registered to course.";
            return(serviceResponse);
        }
 public async Task <IActionResult> AddRegistration(AddRegistrationDTO newRegistration)
 {
     return(Ok(await _registrationService.AddRegistration(newRegistration)));
 }