JIRA: https://jira.spring.io/browse/INT-2879 * Add `id-expression` attribute for the `<int-jpa:retrieving-outbound-gateway>` * Make it mutually exclusive with other `SELECT` attributes * Remove deprecated `max-number-of-results` INT-2879 Polishing - Improve parser error message. - Minor doc polish. INT-2879: Support `delete-after-poll` and `flush`