Fix offer crossing with transfer fee over AMM and other fixes

[gregtatcam]

High Level Overview of Change

This PR addresses three issues:

• Offer crossing with the transfer fee via AMM
• LPToken adjustment to factor in the LPTokenBalance rounding
• Possible conflict between Liquidity Provider trustline LPToken balance and LPTokenBalance when last Liquidity Provider withdraws all tokens

Type of Change

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [x] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] Refactor (non-breaking change that only restructures code)
• [ ] Performance (increase or change in throughput and/or latency)
• [x] Tests (you added tests for code that already exists, or your new feature included in this PR)
• [ ] Documentation update
• [ ] Chore (no impact to binary, e.g. .gitignore, formatting, dropping support for older tooling)
• [ ] Release

Before / After

1. qualityUpperBound() and QualityFunction calculation doesn't factor in the transfer fee on offer crossing. This is correct behavior when crossing an account offer. Single-path with AMM limits the out value based on the limitQuality. If the transfer fee is not factored in then the out value is going to be such that the generated AMM offer quality matches the limitQuality. But the effective quality is smaller because takerPays amount factors in the transfer fee when the strand's quality is calculated. The fix factors in the transfer fee when the quality is adjusted for the fees on offer crossing.
2. adjustAmountsByLPTokens() function is not returning adjusted tokens and amounts in some cases. The fix returns the adjusted LPToken and adjusted amounts.
3. Liquidity Provider's (LP) LPToken trustline balances might not add up to the total LPTokenBalance due to the rounding. This results in a dust amount left in the balances on the last LP withdrawal or the withdrawal transaction failing. The fix sets the LPTokenBalance to the trustline balance if LP is the only remaining LP on withdrawal transaction.

Test Plan

Updated AMM_test and AMMExtended unit-tests.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 91.57895% with 8 lines in your changes are missing coverage. Please review.

Project coverage is 71.1%. Comparing base (2705109) to head (15390be).

Additional details and impacted files

[](https://app.codecov.io/gh/XRPLF/rippled/pull/5016?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=XRPLF) ```diff @@ Coverage Diff @@ ## develop #5016 +/- ## ========================================= + Coverage 71.0% 71.1% +0.1% ========================================= Files 796 796 Lines 66912 66997 +85 Branches 10988 10979 -9 ========================================= + Hits 47540 47635 +95 + Misses 19372 19362 -10 ``` | [Files](https://app.codecov.io/gh/XRPLF/rippled/pull/5016?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=XRPLF) | Coverage Δ | | |---|---|---| | [src/ripple/app/misc/impl/AMMHelpers.cpp](https://app.codecov.io/gh/XRPLF/rippled/pull/5016?src=pr&el=tree&filepath=src%2Fripple%2Fapp%2Fmisc%2Fimpl%2FAMMHelpers.cpp&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=XRPLF#diff-c3JjL3JpcHBsZS9hcHAvbWlzYy9pbXBsL0FNTUhlbHBlcnMuY3Bw) | `97.6% <100.0%> (+0.4%)` | :arrow_up: | | [src/ripple/app/misc/impl/AMMUtils.cpp](https://app.codecov.io/gh/XRPLF/rippled/pull/5016?src=pr&el=tree&filepath=src%2Fripple%2Fapp%2Fmisc%2Fimpl%2FAMMUtils.cpp&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=XRPLF#diff-c3JjL3JpcHBsZS9hcHAvbWlzYy9pbXBsL0FNTVV0aWxzLmNwcA==) | `99.4% <100.0%> (+0.2%)` | :arrow_up: | | [src/ripple/protocol/impl/Feature.cpp](https://app.codecov.io/gh/XRPLF/rippled/pull/5016?src=pr&el=tree&filepath=src%2Fripple%2Fprotocol%2Fimpl%2FFeature.cpp&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=XRPLF#diff-c3JjL3JpcHBsZS9wcm90b2NvbC9pbXBsL0ZlYXR1cmUuY3Bw) | `93.9% <ø> (ø)` | | | [src/ripple/app/paths/impl/BookStep.cpp](https://app.codecov.io/gh/XRPLF/rippled/pull/5016?src=pr&el=tree&filepath=src%2Fripple%2Fapp%2Fpaths%2Fimpl%2FBookStep.cpp&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=XRPLF#diff-c3JjL3JpcHBsZS9hcHAvcGF0aHMvaW1wbC9Cb29rU3RlcC5jcHA=) | `93.1% <95.0%> (+1.1%)` | :arrow_up: | | [src/ripple/app/tx/impl/AMMWithdraw.cpp](https://app.codecov.io/gh/XRPLF/rippled/pull/5016?src=pr&el=tree&filepath=src%2Fripple%2Fapp%2Ftx%2Fimpl%2FAMMWithdraw.cpp&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=XRPLF#diff-c3JjL3JpcHBsZS9hcHAvdHgvaW1wbC9BTU1XaXRoZHJhdy5jcHA=) | `91.2% <66.7%> (+0.8%)` | :arrow_up: | ... and [2 files with indirect coverage changes](https://app.codecov.io/gh/XRPLF/rippled/pull/5016/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=XRPLF) [](https://app.codecov.io/gh/XRPLF/rippled/pull/5016?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=XRPLF)