Todo: deprecate `paid` field in `MintQuote`

[callebtc]

It's not part of the spec, we keep it around for legacy clients. Let's break them.

[KvngMikey]

@callebtc 😅, been trying to work on this for days, feel like i've finally removed the paid field from mintQuote, most of the tests are failing now, is this breaking change meant to break them too or should i keep going at fixing them?

also, are we going to raise a separate issue to deprecate paid field in meltQuote or that isn't needed ?