```

`OAuth2PasswordRequestForm` is a class dependency that declares a form body with:

* The `username`.
* The `password`.
* An optional `scope` field as a big string, composed of strings separated by spaces.
* An optional `grant_type`.

!!! tip
    The OAuth2 spec actually *requires* a field `grant_type` with a fixed value of `password`, but `OAuth2PasswordRequestForm` doesn't enforce it.