set min/max correctly when values are zero [MRXN23-559]

[hotzevzl]

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Overview

Fix my own 🤦🏼 bug that broke stuff because of an improper reliance on falseish values.

Designs

N/A

Testing instructions

There's a new unit test file, which I believe captures most of the logic and edge cases, including the sad-trombone bug in my previous implementation.

Feature relevant tickets

https://vizzuality.atlassian.net/browse/MRXN23-559

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Checklist before submitting

• Meaningful commits and code rebased on develop.
• If this PR adds feature that should be tested for regressions when
  deploying to staging/production, please add brief testing instructions
  to the deploy checklist (docs/deployment-checklist.md)
• Update CHANGELOG file

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Name	Status	Preview	Comments	Updated (UTC)
marxan	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Jan 18, 2024 2:32pm

[hotzevzl]

@KevSanchez the issue here was a classical PEBKAC on my end:

let minResult = feature?.amountMin ? feature?.amountMin : null;
let maxResult = feature?.amountMax ? feature?.amountMax : null;

This is obviously going to result in a loud sad-trombone fail sound when feature.amountMin === 0 or feature.amountMax === 0.

Since my being a bad person didn't stop at this bug but also at sticking more and more code inside of the already-inflated ProjectsService class, I took this opportunity for atonement, moving the conversion function to its own corner of the source tree, not least to make unit-testing it easier (and I included indeed unit tests that also stress the bug I believe to have fixed).

[KevSanchez]

To be fair, I would have followed the exact same assumption; another stark reminder of the dangerous subtleties of javascript :\