Confusing naming of function passed to Array.map

Hello,
not a real issue but just a naming of a method that confused me for a bit.
In [datasource/launch](https://github.com/apollographql/fullstack-tutorial/blob/master/final/server/src/datasources/launch.js#L10) there is method called `launchReducer` passed to `Array.map`. This method is responsible to take each launch returned by the Rest API and **mapping** it to another object.
So I guess this function should be called `lauchMapper`, because that's what it does. It doesn't reduce multiple element into a single one, isn't it?

Just highlighting this because it is a bit confusing

final/server/src/datasources/launch.js の launchReducer 定義を開き、Array.map に渡されている箇所を確認します。関数への他の参照がないか確認し、その後、関数名がマッピングの役割を反映するように命名を一貫して更新します。

索引モデルが issue の本文から書いたものです。