code: @Override
      public CreateAliasResult createAlias(CreateAliasRequest request) {
          request = beforeClientExecution(request);
          return executeCreateAlias(request);
      }
docs: <p>
  Creates an alias for a directory and assigns the alias to the directory. The alias is used to construct the
  access URL for the directory, such as <code>http://&lt;alias&gt;.awsapps.com</code>.
  </p>
  <important>
  <p>
  After an alias has been created, it cannot be deleted or reused, so this operation should only be used when
  absolutely necessary.
  </p>
  </important>
  
  @param createAliasRequest
  Contains the inputs for the <a>CreateAlias</a> operation.
  @return Result of the CreateAlias operation returned by the service.
  @throws EntityAlreadyExistsException
  The specified entity already exists.
  @throws EntityDoesNotExistException
  The specified entity could not be found.
  @throws InvalidParameterException
  One or more parameters are not valid.
  @throws ClientException
  A client exception has occurred.
  @throws ServiceException
  An exception has occurred in AWS Directory Service.
  @sample AWSDirectoryService.CreateAlias
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/ds-2015-04-16/CreateAlias" target="_top">AWS API
  Documentation</a>