Triple furness post

[isaac-tfn]

Include the option to run a triply constrained furness when running a gravity model post-calibration.

The third constraint is to the distribution bins, which can overfit. This is partly mitigated by an xamax parameter for the run method which limits how much the achieved distribution can be moved by the triple furness, but it should also not be standard procedure to use this, possibly only for particularly poorly fitting distributions.

Task Checklist

• [ ] Have unittests been added (testing individual functions and their edge cases)
• [ ] Have integration tests been added (if applicable, to test modules of functionality)
• [ ] Updated RELEASE.md to reflect changes in PR
• [ ] Have new dependencies been added?
  • [ ] Have they been added to either requirements.txt or requirements_dev.txt.
  • [ ] Have they been added to setup.cfg

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📚 Documentation preview 📚: https://cafdistribute--28.org.readthedocs.build/en/28/

[codecov[bot]]

Codecov Report

Attention: 177 lines in your changes are missing coverage. Please review.

Comparison is base (30e4c8c) 85.09% compared to head (7b9c61e) 73.21%. Report is 101 commits behind head on main.

Files	Patch %	Lines
src/caf/distribute/gravity_model/multi_area.py	72.72%	63 Missing :warning:
src/caf/distribute/furness.py	18.03%	50 Missing :warning:
src/caf/distribute/gravity_model/core.py	52.85%	33 Missing :warning:
src/caf/distribute/gravity_model/single_area.py	82.75%	20 Missing :warning:
src/caf/distribute/utils.py	52.17%	11 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #28 +/- ## =========================================== - Coverage 85.09% 73.21% -11.89% =========================================== Files 7 9 +2 Lines 416 769 +353 =========================================== + Hits 354 563 +209 - Misses 62 206 +144 ```

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