Provide remote channel public keys to signer

[devrandom]

This allows the signer to verify that the per-tx public keys are correctly derived from our keys and the remote pubkeys/basepoints.

Also, should we use ChannelPublicKeys to group the remote pubkeys in Channel?

[TheBlueMatt]

Also, should we use ChannelPublicKeys to group the remote pubkeys in Channel?

Yea, if we're gonna have a struct for it, would probably be nice to use it in the Channel itself IMO.

[devrandom]

OK, the struct is now used in Channel.

[TheBlueMatt]

Looking good. Not a big fan of he new funding_pubkey wrapper, but its not a huge deal.

[devrandom]

(sorry for multiple notifications on the unwrap comment, github is having an issue. I'm not able to attach this to the actual comment anymore)

How about if we rename this to their_unwrapped_funding_pubkey?

This does reduce verbosity in four callsites.

[TheBlueMatt]

Hmmm, alright, I mean it doesn't matter tooo much cause there's a number of things that are only available after they provide an accept_channel....

[devrandom]

Right, things will be cleaner once the InboundChannel / OutboundChannel is implemented.

[TheBlueMatt]

Looks good. Just two small nits. I went ahead and squashed for review anyway, and added demo comments at https://github.com/TheBlueMatt/rust-lightning/tree/2020-01-451-nits so feel free to just take that branch and I'll merge.