This PR has turned into a bit of a big refactoring, sorry for the large diff

On the plus side it does now solve #80 and #37 and touches on addressing Liams comments in #47

Codecov Report

Attention: Patch coverage is 97.19626% with 6 lines in your changes are missing coverage. Please review.

Project coverage is 95.74%. Comparing base (64e4aa1) to head (bbdb65c).
Report is 6 commits behind head on main.

❗ Current head bbdb65c differs from pull request most recent head e860a74. Consider uploading reports for the commit e860a74 to get more accurate results

@@            Coverage Diff             @@
##             main      #89      +/-   ##
==========================================
- Coverage   95.96%   95.74%   -0.23%     
==========================================
  Files           7        5       -2     
  Lines         347      235     -112     
==========================================
- Hits          333      225     -108     
+ Misses         14       10       -4     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

tests are passing locally and on CI
the examples are running locally and on CI

only missing code coverage now

This PR is currently reducing the package by a reasonable amount of lines of code while also adding functionality.

I've redone the checking of values so that it is more concise as mentioned by @RemDelaporteMathurin

I'm keen to see if this issue can be fixed before we bring in nesst as a dependency

I just noticed another part of the code that will need changing to support DD and DT reactions. It looks like this part is only considering DT reactions

So we might need to add DD reactions

Also I guess the ion_density for DD pairs is also half that of DT pairs

@RemDelaporteMathurin do you remember why this is ion_density**2 here in the code?

closing in favour of #95