Compact blinded path creation

[jkczyz]

Add support for creating a compact BlindedPath, which consists of:

• using an SCID instead of a node id in BlindedHop::encrypted_payload
• using IntroductionNode::DirectedShortChannelId

The first is accomplished by specifying SCIDs when calling BlindedPath::new_for_message using a new message::ForwardNode struct. The second is through calling BlindedPath::use_compact_introduction_node. Both are called by DefaultMessageRouter.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 92.19858% with 11 lines in your changes are missing coverage. Please review.

Project coverage is 90.29%. Comparing base (a95338a) to head (e4661fe). Report is 7 commits behind head on main.

Files	Patch %	Lines
lightning/src/ln/offers_tests.rs	81.25%	0 Missing and 6 partials :warning:
lightning/src/blinded_path/mod.rs	86.20%	3 Missing and 1 partial :warning:
lightning/src/util/test_utils.rs	50.00%	1 Missing :warning:

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3011      +/-   ##
==========================================
+ Coverage   89.87%   90.29%   +0.42%     
==========================================
  Files         117      117              
  Lines       96952   100069    +3117     
  Branches    96952   100069    +3117     
==========================================
+ Hits        87134    90357    +3223     
+ Misses       7273     7130     -143     
- Partials     2545     2582      +37     

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[jkczyz]

Rebased

[jkczyz]

LGTM pending maybe making the compact encoding optional. Looks like it needs another rebase as well.

Rebased now. Yeah, maybe best to do that in a follow-up as it may be a little more involved. Let me know if you have any thoughts on https://github.com/lightningdevkit/rust-lightning/pull/3011#discussion_r1600386890.

[TheBlueMatt]

Feel free to squash and we can land this IMO. We should open an issue and block the next release on the followup.

[jkczyz]

Feel free to squash and we can land this IMO. We should open an issue and block the next release on the followup.

Rebased and opened #3080. Looking for feedback on the ChannelManager API (see https://github.com/lightningdevkit/rust-lightning/pull/3011#discussion_r1610736336).

[jkczyz]

Added derives to ForwardNode.