if trampoline is used, prioritize mpp_splits that use the same trampoline

[ecdsa]

If trampoline is used, mpp_split should prioritize solutions that send HTLCs to the same trampoline.
This will reduce fees, and also reduce the probability of failure.

[ecdsa]

@bitromortac

[bitromortac]

The issue with payment indexing was fixed in eclair, see ACINQ/eclair#1723.

electrum/electrum/lnworker.py

Lines 1526 to 1530 in 9c1a515

	# for trampoline mpp payments we have to restrict ourselves to pay
	# to a single node due to some incompatibility in Eclair, see:
	# https://github.com/ACINQ/eclair/issues/1723
	use_singe_node = not self.channel_db and constants.net is constants.BitcoinMainnet
	split_configurations = suggest_splits(amount_msat, channels_with_funds, single_node=use_singe_node)

This should be no longer relevant and we could test sending via different trampoline nodes.