In most cases, it's the same as option_anchor_outputs, but for
fees it's different. This transformation is the simplest:
pass it as a pair, and test it explicitly.
In future we could rationalize some paths, but this was nice
and mechanical.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
for every new added htlc, check that adding it won't go over our 'dust
budget' (which assumes a slightly higher than current feerate, as this
prevents sudden feerate changes from overshooting our dust budget)
note that if the feerate changes surpass the limits we've set, we
immediately fail the channel.
HTLC fees increase (larger weight), and the fee paid by the opener
has to include the anchor outputs (i.e. 660 sats).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
