Token server features

[tomt1664]

Currently the token-server supports the swiss-pay API in order to enable payments for tokens that a validated for use in the mainnet mercury layer server.

We want to add features to enable making the payment directly to a connected bitcoin or lightning node.

So in the config, the user will be able to choose between, swisspay, lightning or bitcoin node (or both ln and bitcoin). The bitcoin rpc credentials will need to be supplied, and also a RTL lightning node url and macaroon.

The functions to enable this were previously implemented in the old mercury server: https://github.com/commerceblock/mercury/blob/master/server/src/protocol/pay_on_deposit.rs