[Feature] RPC method to query whether a record has been published in a transaction.

[kellpossible]

🚀 Feature

A new RPC method to efficiently query whether a record serial number has been published in a transaction, and which transaction that was.

Input:

• Record serial number.

Output:

• Optional of transaction id. (Returns null if the record has not been published. Returns the transaction id that the record was published in if it was published).

Motivation

I want to check whether a particular record has been spent in a transaction, to see if it can be used in a new transaction. Perhaps there is a different way to accomplish this efficiently using the current API that I haven't considered yet.