public async Task ExecuteAsync(string name, string email)
{
var existingTrainer = await _trainerRepository.GetByEmailAsync(email);
if (existingTrainer is null)
{
var trainer = new Trainer(name, email);
_trainerRepository.Create(trainer);
await _trainerRepository.UnitOfWork.SaveChangesAsync();
}
else
{
throw new InvalidOperationException("The email is already being used.");
}
}