[feature]: Use more sophisticated margin for invoice acceptor

[GeorgeTsagk]

Background

Currently our invoice acceptor for lightning payments has some room for error for the amount sent by the sending party. Due to inaccuracies that may be produced by translating an asset to msat, we want to still accept invoices that are slightly off.

For assets with very high value this behavior may be taken advantage of by malicious senders, as they may try to abuse this artificial breathing room to their advantage.