Add new schema for static linear model and enforce model schemas

[alexdewar]

This PR adds a new v2 schema for the static linear model, which adds the various trend-related fields. If you could check that the constraints I've chosen seem sensible (e.g. does anything need a max/min value property?) that would be great. Besides that, I don't think any of the other schemas need new versions yet (though see #531), but if I've missed any, please let me know!

I've added the code to enforce these schemas at model load time. I did a small amount of refactoring to facilitate this (mostly amalgamating the static and dynamic model loading functions).

Closes #529. Closes #530.

[codecov]

Codecov Report

Attention: Patch coverage is 3.92157% with 49 lines in your changes missing coverage. Please review.

Project coverage is 48.72%. Comparing base (9a6e7e3) to head (f69234c).
Report is 7 commits behind head on main.

Files with missing lines	Patch %	Lines
src/HealthGPS.Input/model_parser.cpp	0.00%	49 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #532      +/-   ##
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- Coverage   48.82%   48.72%   -0.11%     
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  Files         164      164              
  Lines        7779     7795      +16     
  Branches     1059     1063       +4     
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  Hits         3798     3798              
- Misses       3972     3988      +16     
  Partials        9        9              

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[jamesturner246]

No, I think the schema seems sensible. Depending on if you want to, strictly speaking a number of the numbers cannot be negative. For instance stddevs, prevalence, but this covers the majority of it. Up to you.

Else LGTM 👍
Usual questions

[jamesturner246]

No need to worry about it for now, but will it be possible eventually to load older configs using older schemas? For instance by using the config's schema version directly?

[alexdewar]

Yep, that's the plan. Atm I'm not requiring the $schema attribute, but we could do. I was just thinking that we could try to validate a file with the newest version of the schema and if that doesn't work, we try the next oldest etc.

[jamesturner246]

To be clear, this isn't used anywhere right now, right?

[alexdewar]

I should have said, but no, it's not used by HGPS. I do use static.json and dynamic.json for validating config files in healthgps-examples, but in HGPS I load the model schemas directly because you get clearer error messages that way.