code: public static Validator<CharSequence> domainName(@NonNull final Context context) {
          return new DomainNameValidator(context, R.string.default_error_message);
      }
docs: Creates and returns a validator, which allows to validate texts to ensure, that they
  represent valid domain names. Empty texts are also accepted.
  
  @param context
  The context, which should be used to retrieve the error message, as an instance of
  the class {@link Context}. The context may not be null
  @return The validator, which has been created, as an instance of the type {@link Validator}