Update expensify_prod branch

[nathanmetcalf]

Will self-merge, this code has already been peer reviewed.

[melvin-bot]

I see this code uses list. If your primary use case is just checking to see if an item exists in the list, perhaps set is a better choice, as it's much faster for random access. C++ has a variety of data structures available to choose from, so pick the best for your use case.