Ergonomics

Before I stated that we shouldn't treat each function as its own unit of work—it's way too verbose and it leads to a lot of noise in the logs.
Nonetheless, it is often the case that a unit of work maps to a certain function. The work starts when that function is invoked and ends when it returns. That was indeed the case in the previous exercise.

When it happens, we can use the instrument macro to avoid having to manually create a span inside the function body.