feat(cardano): validate pool registration owner witness path

[davidmisiak]

Adds validation of witness request path against the path in the pool registration certificate, as proposed by @janmazak.

[gabrielKerekes]

I'm not sure we actually need the PoolOwnerPathChecker.

The owner and witness paths are already checked in the AccountPathChecker. Yes, it only compares accounts, but that's enough for staking paths as they have to end with /2/0 (given by SCHEMA_STAKING_ANY_ACCOUNT), and the paths have to follow the schema in both the updated code and in the old code too. So a different staking path would fail in account path checker.

IMHO the only thing we need to add on top of the old code would be validating that there is only one witness request in _validate_stake_pool_registration_tx_structure.

Or am I missing something?

[gabrielKerekes]

Suggested change

	INVALID_STAKEPOOL_REGISTRATION_TX_WITNESS = wire.ProcessError(
	"Stakepool registration transaction can only contain sinlge staking witnesses with the same path as in the certificate"
	INVALID_STAKEPOOL_REGISTRATION_TX_WITNESS = wire.ProcessError(
	"Stakepool registration transaction can only contain a single staking witness and its path must match the certificate owner's path"

[gabrielKerekes]

This test fails because the witness path is not a valid staking path not because it's different from the pool owner path.

[davidmisiak]

Note for future readers: Currently different staking paths aren’t allowed because of the single-account policy and there being only one staking key per account. However when CIP-0018 should be supported on HW wallets this is the implementation for the pool owner witness request path validation.