Rename `Htlc::to_bitcoin_amount` to `satoshi_amount`

[jirijakes]

Per https://github.com/lightningdevkit/rust-lightning/pull/3063#discussion_r1622867330 .

I believe it's soon enough after the method was first introduced that renaming it should not have big negative impact, if any.

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Codecov Report

Attention: Patch coverage is 91.66667% with 1 line in your changes missing coverage. Please review.

Project coverage is 89.96%. Comparing base (e5b7402) to head (ae59eec). Report is 4 commits behind head on main.

Files	Patch %	Lines
lightning/src/ln/chan_utils.rs	80.00%	1 Missing :warning:

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@@            Coverage Diff             @@
##             main    #3099      +/-   ##
==========================================
+ Coverage   89.86%   89.96%   +0.09%     
==========================================
  Files         119      119              
  Lines       97507    98177     +670     
  Branches    97507    98177     +670     
==========================================
+ Hits        87629    88324     +695     
+ Misses       7307     7291      -16     
+ Partials     2571     2562       -9     

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[jirijakes]

@tnull , I called it amount at first (https://github.com/lightningdevkit/rust-lightning/pull/3063#discussion_r1599060322) but I agree with Matt that it might be confusing, given that amount of HTLC has diferent meaning.

The 'satoshi' part should invoke that there will be some rounding happening.

[tnull]

@tnull , I called it amount at first (#3063 (comment)) but I agree with Matt that it might be confusing, given that amount of HTLC has diferent meaning.

The 'satoshi' part should invoke that there will be some rounding happening.

Ah, I had forgotten about that. Given that it really just performs integer division, should we be explicit here and call it floor_amount or amount_floor, similar to, e.g., u32::div_floor?

[TheBlueMatt]

Naming is hard :). I'm a bit meh on floor_amount because it doesn't mention the unit being floor'd to, which I think substantially improves readability of callsites.

[TheBlueMatt]

I believe it's soon enough after the method was first introduced that renaming it should not have big negative impact, if any.

Its not in a release, so there's no impact :)

[tnull]

Naming is hard :). I'm a bit meh on floor_amount because it doesn't mention the unit being floor'd to, which I think substantially improves readability of callsites.

So floor_sats_amount or amount_floor_sats?

[TheBlueMatt]

That would be good with me, or amount_sats_floor or any other permutation :)

[G8XSU]

amount_sats :)