* @return der registrierte Employee, der sich einloggen darf
* @throws RegistrationFailedException Fehlerhafte Registration
*/
public Employee register(RegistrationRequest registrationRequest) throws RegistrationFailedException {
try {
EmployeeData data = new EmployeeData();
data.email = registrationRequest.email;
data.password = registrationRequest.password;
data.department = registrationRequest.department;
data.firstname = registrationRequest.firstname;
data.lastname = registrationRequest.lastname;