Implement proof generation route in the aggregator

[jpraynaud]

Why

In order to give the capability to a client to certify a specific list of transactions, the aggregator needs to generate a proof (of list of proofs) for these transactions.

What

Implement a new route in the aggregator which computes proofs for transactions subset (recreate a Merkle tree from the stored transactions and create a list of Merkle proofs for all the transactions that are included in the tree)

How

• Implement route proof/cardano-transaction that creates proofs for list of transactions
• Update OpenAPI specs