This way the default is still to compile with -Werror, but it allows a
local override in a cabal.project.local file with:

  constraints:
    kupo -production

We need to keep the transactions around until a SnapshotConfirmed will
yield a "block" containing them.

This should make much of a difference, but is a more idiomatic way to
store things by key.

We are re-using the ServerOutput golden files from the hydra repository
to test compatibility with the hydra-node websocket API.

- Stub for TxValid decoder by using empty values (apart from txId)
- Add confirmedTransactionIds parsing for Snapshot

This should already give use enough information to index some UTxO in
the head.

Simulates transactions for each UTxO in the initial snapshot to make
kupo index this "genesis" block.

The decoder is copy & pasted from ogmios with only ada/lovelace needing
replacing. We should DRY this (or change our apis to be compatible).

  So that we remove many elements from the store in a single atomic transaction.

  We do this by skipping blocks because we don't really have much alternative. This is therefore relatively unsound for very long running head. Though is it more sound that actually replaying all events from that head onto an existing database; so it's kind of a best effort solution.