INT-2426: Add `Idempotent Receiver` EIP pattern

JIRA: https://jira.spring.io/browse/INT-2426

**DO NOT MERGE YET**

It's just an initial commit, like a PoC to review before further work.
Should be a `ConcurrentMetadataStore` to support concurrency and clustered environments. Use `putIfAbsent()` for atomicity.