docs: protected void transformUsername(final UsernamePasswordCredential userPass) throws AccountNotFoundException {
          if (StringUtils.isBlank(userPass.getUsername())) {
              throw new AccountNotFoundException("Username is null.");
          }
          LOGGER.debug("Transforming credential username via [{}]", this.principalNameTransformer.getClass().getName());
          val transformedUsername = this.principalNameTransformer.transform(userPass.getUsername());
          if (StringUtils.isBlank(transformedUsername)) {
              throw new AccountNotFoundException("Transformed username is null.");
          }
          userPass.setUsername(transformedUsername);
      }