Explain difference between RequiresContext and IoC containers

It is not clear from the documentation when you'd select to use `RequiresContext` instead of an IoC container.
We should explain the differences and demonstrate the different usecases where one is better over the other.

Start by locating the documentation for RequiresContext and any existing references to IoC containers in the repository. Compare the concepts and examples already present; done means the documentation clearly explains when to choose each approach and demonstrates use cases where one is preferable.

索引モデルが issue の本文から書いたものです。