Extract SQL queries to a separate module

[jonathan-d-zhang]

Currently at least a few DB functions are repeated (looking up a package, for example). Extracting these queries to a separate module will let us deduplicate and isolate (SQL) security issues to one spot.

I think we can do all the queries at once. The amount of refactoring necessary should be smaller, and it will be easier to manage

[jonathan-d-zhang]

Now thinking about this again, it doesn't make sense to have it separate from #295.