Make it optional to generate test with model

[jacobconley]

Description

Hello! The model generator is great but it always generates a test in the same directory, which isn't ideal for all use cases (not mine at least). I'd like to disable it altogether, though I imagine some other folks may just wish to put them in another directory.

I'd be happy to submit a pull request that does this if there's interest - I could just split up this call to .Box() into two right?

Steps to Reproduce the Problem

Generate a model using the Soda CLI or anything else that uses Pop's model generator

Expected Behavior

Exactly what happened, but it would be nice to be able to disable the generation of the test file that's generated alongside the requested model