/**
  * Initializes the resolver. Calling {@link this#resolve()} will actually resolve the users and
  * creates them if necessary.
  *
  * @param userFactory User factory used to create new users
  * @param roleConverter Role converter class
  * @param producer Producer identifier
  * @param consumer Consumer identifier
  */
 public UserResolver(
     UserFactory<USER, ROLE> userFactory,
     RoleConverter<ROLE> roleConverter,
     UserIdentifier producer,
     UserIdentifier consumer) {
   this.userFactory = userFactory;
   this.producerRoleContainer = RoleContainer.forProducer(producer, roleConverter);
   this.consumerRoleContainer =
       RoleContainer.forConsumer(consumer, producerRoleContainer, roleConverter);
 }