Simplify Bolt11 Payments and Remove Redundant Code

[shaavan]

resolves #3262
builds on: #3342

Summary

This PR introduces pay_for_bolt11_invoice, simplifying how Bolt11 payments are processed by allowing direct invoice-based payments while still enabling custom routing parameters. With this change, the redundant bolt11_payment.rs utility functions are no longer needed and have been removed.

Why This Change?

• Previously, paying a Bolt11 invoice required manually extracting payment_id, payment_hash, and other parameters before passing them to send_payment.
• pay_for_bolt11_invoice introduces a more streamlined approach, mirroring the existing convenience of Bolt12 payments.
• With this function now handling parameter extraction within ChannelManager, bolt11_payment.rs is redundant and can be safely removed.

Changes

• Introduced pay_for_bolt11_invoice:
  • Takes a Bolt11 invoice directly.
  • Allows users to set custom routing parameters via RouteParametersConfig.
• Removed bolt11_payment.rs:
  • All relevant logic is now handled within ChannelManager.
  • Removed associated test cases for redundant utility functions.

Impact

• Reduces complexity for Bolt11 payments.
• Cleans up redundant code, making the implementation more maintainable.

[TheBlueMatt]

Thanks! This needs rebase now.

[shaavan]

Updated from pr3617.01 to pr3617.02 (diff):

Changes:

1. Rebase on main.

[shaavan]

Updated from pr3617.02 to pr3617.03 (diff):
Addressed @TheBlueMatt comments

Changes:

1. Introduce payment_id as parameter, and update documentation

[codecov]

Codecov Report

Attention: Patch coverage is 84.50704% with 11 lines in your changes missing coverage. Please review.

Project coverage is 88.57%. Comparing base (1610854) to head (16368c0).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
lightning/src/ln/outbound_payment.rs	81.57%	3 Missing and 4 partials ⚠️
lightning/src/events/mod.rs	0.00%	2 Missing ⚠️
lightning/src/routing/router.rs	86.66%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3617      +/-   ##
==========================================
- Coverage   88.60%   88.57%   -0.03%     
==========================================
  Files         151      150       -1     
  Lines      118454   118377      -77     
  Branches   118454   118377      -77     
==========================================
- Hits       104957   104856     -101     
- Misses      10985    10990       +5     
- Partials     2512     2531      +19     

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[TheBlueMatt]

thanks!

[jkczyz]

Won't this break downgrades? We need to map to a variant available prior to version 0.0.124. I guess it is never serialized in an event, and instead return directly? I wonder if we should make a Bolt11PaymentError similar to Bolt12PaymentError instead.

[TheBlueMatt]

Oops, right.

We def could add a Bolt11PaymentError, tho it seemed like way too much complexity for one variant to me 🤷

[shaavan]

Thanks a lot for the pointer! Updated in pr3617.04
I think it makes sense that we introduce a new Bolt11PaymentError, as its more 'proper' error type, and also will be useful incase the enum expands in future.

tho it seemed like way too much complexity for one variant to me

After, introducing the variant, I think I was able to get it to work, while keeping the complexity manageable!
Let me know if it looks good! Thanks!

[shaavan]

Updated from pr3617.03 to pr3617.04 (diff):
Addressed @jkczyz comments

Changes:

1. Introduce new variant Bolt11PaymentError, to not break downgrades.
2. Move the relevant test from bolt11_payment.rs, to the codebase, to keep the test suite exhaustive.

[shaavan]

Updated from pr3617.04 to pr3617.05 (diff):
Addressed @jkczyz comment

Changes:

1. Introduce explicit check for failure case in the introduced test.