input method
Get request value
req.input('email');
A dot key reads inside maps and lists, like user.name or
items.0.id. A key that is in the input as it is wins.
defaultValue is given when the key is not there or is null.
req.input('user.name', 'guest');
Implementation
@override
dynamic input(String key, [dynamic defaultValue]) {
return _find(key).value ?? defaultValue;
}