fix: register custom config model

[alohamora]

Description

This PR fixes the bug where foca did not register a custom config model which is passed in the input config if the api specs were not provided.
In addition, the validator for model path also converts the relative path passed in the config.yaml to the absolute path because casbin is not able to resolve relative path directly.

Fixes #181

Type of change

• Bug fix (non-breaking change which fixes an issue)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (80f0136) 100.00% compared to head (9693596) 100.00%.

Additional details and impacted files

@@            Coverage Diff            @@
##               dev      #189   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files           20        20           
  Lines          978       984    +6     
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+ Hits           978       984    +6     

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[alohamora]

@uniqueg I couldn't figure out on how to add tests for this specific change as it is just reading the model field from the config and converting it to an absolute path. I have tested this by manually passing model from cloud-registry and it is working fine.
Let me know how to handle testing for this

[uniqueg]

This is a very elegant fix, thanks a lot

[uniqueg]

I have just seen the comment about the tests. I guess you could simply test it by instantiating the model with None, with a relative path, with an absolute path and with an invalid/non-existing path.

If you can add those tests and they pass, you can just go ahead and merge it. I don't think there will be a need for another review.

If you still have trouble writing the tests, just text in the #foca channel on Slack and I'll help you :)

[alohamora]

Hey @uniqueg can you please review the PR again, I was not confident if I was adding tests the correct way :)
Also, I did a small change of normalizing the relative paths which use .. notation by using Pathlib.resolve() method instead of manually constructing absolute path.