This splits the overall example rack service into many sub-services.
This leads to a much cleaner factoring of the code. Note that there are
some missing properties -- it's hard to eyeball this without a real compiler.
But the essence of the example is pretty spot on.
I personally prefer this syntax. It is more "declarative" and, particularly
because we support true assignments, I feel like it's more representative of
what's going on. It's easier to scan for real imperative assignments. This
approach also eliminates a single horizontal character per assignment.
In this change, ":= new" declares a new resource.
In addition, we change arrays to be Go-like, in that zero-initialized
ones can be appended to safely, such that declaring a new instance is
done merely by stating "var arr: T[]".
