Field names on Schemas not cleaned

The Schema for this can be found in this issue
https://github.com/tazatechnology/openapi_spec/issues/58
The issue here is that a field is being named 
```dart
/// No Description
@JsonKey(name: r'r@nd0m_$t#ff', includeIfNull: false) String ? r@nd0m$t#ff,
```
Which is invalid text for a dart variable