We need this ticket to solve the following issue:

We run two separate parity-db instances - one for substrate storage, one for ledger storage. We store the merkle root for the current ledger state in substrate storage.

ParityDB requires a graceful shutdown, otherwise Ledger states may not get committed before the node process exits. When the node starts up again, it fails to find the ledger state root in the ledge storage parity db instance.

PR open: #1278
Relates to https://github.com/midnightntwrk/midnight-security/issues/66

Requires merge and release of: midnightntwrk/midnight-ledger#430