code: @Deprecated
      public FeatureState addUsers(Collection<String> users) {
          Set<String> set = new LinkedHashSet<>();
          set.addAll(this.getUsers());
          set.addAll(users);
          String setAsString = Strings.trimToNull(Strings.join(set, ","));
          setParameter(UsernameActivationStrategy.PARAM_USERS, setAsString);
          return this;
      }
docs: Adds a single user to the list of users
  
  @deprecated This method will be removed soon. Use {@link #setParameter(String, String)} instead to modify the
  corresponding strategy parameter.