This attempts to solve a problem we have with Phoenix clients:
This payment has been split in two many parts by the sender: 31 parts vs max 6 parts allowed for on-the-fly funding.
The problem is that we don't have any way in bolt11 or bolt12 to
specify the maximum number of HTLCs.
As a workaround, we start by restricting askrene to 6 parts if the
node is not openly reachable, and if it struggles, we remove the
restriction. This would work much better if askrene handled maxparts
more completely!
See-Also: https://github.com/ElementsProject/lightning/issues/8331
Changelog-Fixed: `xpay` will not try to send too many HTLCs through unknown channels (6, as that is Phoenix's limit) unless it has no choice
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
73147dafe2