Add phase transfer reactions

[boulderdaze]

This PR adds ReversibleRateConstant class and HenrysLawCoefficient class.
Those two classes are written based on the MIAM README example, and I have a few questions:

1. k_r, is a parameter in `ReversibleRateConstant, which represents the reverse rate constant. Is it okay that this value comes from the configuration, assuming as a fixed value?
2. henrys law coefficient is calculated assuming that it is diprotic acids. Should this class be more generalized instead of relying on that specific assumption?

[Copilot]

Pull request overview

This PR adds support for phase transfer reactions by introducing two new classes: HenrysLawCoefficient for calculating effective Henry's Law coefficients accounting for diprotic acid dissociation, and ReversibleRateConstant for modeling reversible reactions with temperature-dependent equilibrium constants. The PR also extends the Conditions struct with an optional pH field to support pH-dependent transfer coefficient calculations.

Key Changes

• Introduced HenrysLawCoefficient class that calculates effective Henry's Law coefficients with support for temperature dependence and acid dissociation equilibria (K_a1 and K_a2)
• Added ReversibleRateConstant class for computing forward rate constants from equilibrium constants and reverse rate constants
• Extended Conditions struct with std::optional<double> pH to support pH-dependent calculations

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
include/micm/process/transfer_coefficient/henrys_law_coefficient.hpp	New header implementing effective Henry's Law coefficient calculations for diprotic acids with pH and temperature dependence
include/micm/process/rate_constant/reversible_rate_constant.hpp	New header implementing reversible rate constant calculations using equilibrium constant approach
test/unit/process/transfer_coefficient/test_henrys_law_coefficient.cpp	Comprehensive unit tests for Henry's Law coefficient including pH dependence, temperature dependence, and edge cases
test/unit/process/rate_constant/test_reversible_rate_constant.cpp	Comprehensive unit tests for reversible rate constant covering temperature dependence and various equilibrium scenarios
test/unit/process/transfer_coefficient/CMakeLists.txt	New CMake configuration to build Henry's Law coefficient tests
test/unit/process/rate_constant/CMakeLists.txt	Added test target for reversible rate constant
test/unit/process/CMakeLists.txt	Added transfer_coefficient subdirectory to build system
include/micm/system/conditions.hpp	Added optional pH field to support pH-dependent transfer coefficients
include/micm/Process.hpp	Updated to include new headers for reversible rate constant and Henry's Law coefficient

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[codecov-commenter]

Codecov Report

❌ Patch coverage is 94.28571% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.37%. Comparing base (fa5c5ec) to head (017222f).

Files with missing lines	Patch %	Lines
...process/rate_constant/reversible_rate_constant.hpp	86.66%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #887      +/-   ##
==========================================
- Coverage   94.37%   94.37%   -0.01%     
==========================================
  Files          63       65       +2     
  Lines        3163     3198      +35     
==========================================
+ Hits         2985     3018      +33     
- Misses        178      180       +2     

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[K20shores]

1. k_r, is a parameter in `ReversibleRateConstant, which represents the reverse rate constant. Is it okay that this value comes from the configuration, assuming as a fixed value?

To the best of my understanding, it is correct for it to be fixed. I'm under the impression the reversible values are reached assuming the reaction is in a steady-state. But if I'm wrong, we can always change the code.

2. henrys law coefficient is calculated assuming that it is diprotic acids. Should this class be more generalized instead of relying on that specific assumption?

I don't know. Let's assume for now that this is appropriate. We can make a discussion for this after this PR is merged and see if we can get some time from Matt to comment on it.

[K20shores]

Yes. We really calculate the effective henry's law constant, as is noted by your variable names. The A parameter is measured at standard temperature and pressure, so 298.15 is the reference temperature. The temperature dependence of henry's law comes from the van't Hoff equation. That equation is integrated to get the final equation for effective henry's law. What we are looking at appears to be a taylor series approximation of that equation of some kind. Again, this is fine for now and we can get more information on it in a discussion and change the code later if we need to

[boulderdaze]

okay, sounds good. I've added those comments to the discussion note.