Additional Tests - Expansion on PetsTable

[lrljoe]

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[lrljoe]

@rappasoft just to update you, I'm doing some final tests before I merge this PR into develop, so I imagine I'll be issuing the PR from develop into master tomorrow evening.

There's a few functional changes for you to look at, which I've covered in the changelog but also writing up some more detail so that you know what you're looking for

I've also rewritten the TestCase to use a local sqlite database rather than memory, as we aren't changing any values in the db as part of the tests, it stand to reason to persist it for now, as it cuts down on the test time immensely.

I've also introduced approx 100 new tests, bringing test coverage for the package from 80% to 92%. I just want to ensure that there no impact from any adjustments to fixing some of the non-comformant typehinting (e.g. returning int rather than bool in places).