[CAD-3383] Stop processing when snapshot created

[EncodePanda]

Improvement to the --store-ledger functionality. It stops the blockchain processing once the snapshot is created.

[dnadales]

I wonder if we could leave processAll unchanged, and define it in terms of a more general function:

-- | Process all blocks with the given callback until either:
--
-- - The termination condition evaluates to True
-- - There are no more blocks left.
--
processAllUntil ::
     forall blk b st. HasHeader blk
  => Either (ImmutableDB IO blk) (ChainDB IO blk)
  -> ResourceRegistry IO
  -> BlockComponent blk b
  -> st
  -> (st -> b -> IO st)
  -- ^ State transforming function (callback).
  -> (st -> b -> st -> Bool)
  -- ^ Early-termination condition.
  --
  -- The first parameter is the termination condition is the state prior to
  -- applying the given state transforming function. The second parameter is
  -- the block to which this state transforming function is applied, and the
  -- third parameter is its result.
  -> IO st

processAll db rr blockComponent st callback =
  processAllUntil db rr blockComponent st callback (const . const . const False)

In this way:

• we offer more flexibility to define other stopping conditions (we don't know with which use cases people are going to come with)
• we minimize the changes in the existing functions and present and future duplication (no need to alter the process functions and repeat the same return (Continue, _) pattern)

I also wonder, should the termination condition be an IO action as it is now, or do we want to keep it pure?

[EncodePanda]

@dnadales I've went with different approach. Introduced processAllUntil with a general callback function. Then processAll is build on top of it, and processAll_ is build on top of processAll. Let me know what you think.

[nfrisby]

One last UX suggestion (which we chatted about before). Otherwise LGTM. Approved.

[EncodePanda]

bors merge

[iohk-bors]

Build succeeded:

• buildkite/ouroboros-network
• ci/hydra:Cardano:ouroboros-network:required