[feature]: Phase out Legacy Payments

[ziggie1984]

Eclair and LDK stopped accepting legacy payments (payments without a payment_secret (payment_addr in lnd)). This can cause the LND mission_control system to fail the corresponding node because nodes not accepting Legacy Payment report the INVALID_ONION_PAYLOAD failure which causes our node to fail the complete node because we anticipate we did construct a right onion package.

lnd/routing/result_interpretation.go

Lines 383 to 384 in 84c91f7

	case *lnwire.InvalidOnionPayload:
	reportNode()

[ziggie1984]

Maybe instead of removing these payments make the MPP case default for all cases, and only with a special flag allow users to create legacy payments. Currently queryroutes or buildroute will not add a MPP record by default.

[ziggie1984]

Hmm actually this might also be a bug from our side looking at the node_announcment of eclair they clearly state:

  "14": {
                "name": "payment-addr",
                "is_required": true,
                "is_known": true
            }