Configurable Validators

[elijahbenizzy]

This allows us to configure validation on the per-node level. Done at config-time, this sets us up to determine how to add a validator from passed in configuration.

[Short description explaining the high-level reason for the pull request]

Changes

How I tested this

Notes

Checklist

• PR has an informative and human-readable title (this will be pulled into the release notes)
• Changes are limited to a single goal (no scope creep)
• Code passed the pre-commit check & code is left cleaner/nicer than when first encountered.
• Any change in functionality is tested
• New functions are documented (with a description, list of inputs, and expected output)
• Placeholder code is flagged / future TODOs are captured in comments
• Project documentation has been updated if adding/changing functionality.

[elijahbenizzy]

Thoughts:

1. Do we want to enable a per-data-quality check? Currently this is per-node. I like it this way as the API is simpler, but it could get annoying if just one check is breaking.
2. What if there's a node named 'global'? (it shouldn't be a function, and can't be a kwarg...). So I'm ok with there not being one)
3. Need to add more tests

Re: (1) I think we can add an extra field later for this (or add a subfield for check name) but otherwise I'm pretty happy with this. The tricky part is that checks don't have identifiable names...

[skrawcz]

this file needs to be merged into the main docs...

[skrawcz]

(same with basics.md)

[elijahbenizzy]

Yep was waiting for the docs rewrite -- was planning to chop this commit then copy/paste.

[elijahbenizzy]

Ok, I'm going to think through this API this weekend -- feel more confident about the others so i might hold off on this for a bit