Link `Credential` authentication request to proof of scarce asset ?

The current staking credential issuance flow sounds to suffer from the current vulnerability:
- an Issuer announce a destination pubkey Y to be paid on-chain
- a Requester wallet pay the destination pubkey with a Tx A
- the Tx A is observed on-chain and correlated with Issuer policy destination pubkey Y
- the Credentials are issued for the observer instead of the on-chain honest payer

The credentials asset proof could be linked to the on-chain transaction, e.g BIP322.

The issue names no files, tests, or entry points. Start by reviewing the staking credential issuance flow and the proposed BIP322 transaction linkage; done would require an agreed authentication binding that prevents credentials being issued to an observer rather than the payer.

Written by the indexing model from the issue text.