Support user-generated RFQ on tchrpc.SendPayment

[GeorgeTsagk]

Closes #1215

[coveralls]

Pull Request Test Coverage Report for Build 12156853306

Details

• 0 of 69 (0.0%) changed or added relevant lines in 1 file are covered.
• 30 unchanged lines in 7 files lost coverage.
• Overall coverage decreased (-0.07%) to 40.826%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
rpcserver.go	0	69	0.0%

Files with Coverage Reduction	New Missed Lines	%
tappsbt/create.go	2	53.22%
tapchannel/aux_leaf_signer.go	3	43.43%
commitment/tap.go	3	84.7%
universe/interface.go	4	51.95%
tapdb/universe.go	4	80.91%
asset/mock.go	6	91.73%
asset/asset.go	8	80.79%

Totals
Change from base Build 12141057283:	-0.07%
Covered Lines:	25782
Relevant Lines:	63151

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💛 - Coveralls

[guggero]

Very nice! Simple enough approach. Have two suggestions though, otherwise looks good, thank you 🎉

[ffranr]

I think Oli has a good point and that we should pass in the RFQ quote ID and not the SCID. I think that would be clearer, see comment thread.

[guggero]

LGTM 🎉