I'm a little torn on this solution. Mainly because there are times that I want that param nilable, and times where I don't.

I've gotten by so far by requiring the params one way or another by using `Hash#fetch`.

```ruby
content.fetch(:email) # fail fast if this in't supplied
context[:email]           # I don't care it's not present
```

Using `context.email` seems like it'd have to choose one or another. Always return nil or always raise an error.