getUtxoByIntentHash
abstract suspend fun getUtxoByIntentHash(intentHash: String, outputIndex: Int): UnshieldedUtxoEntity?
Get UTXO by intentHash and outputIndex.
Used when processing spentUtxos from the subscription, which returns intentHash instead of transactionHash. We need to find the UTXO's id (which is transactionHash:outputIndex) to mark it as spent.