Missing `autocomplete` attributes on auth pages

Getting this warning in the console on auth pages created by `yarn cedar g dbAuth`

```
[DOM] Input elements should have autocomplete attributes (suggested: "username"): (More info: https://goo.gl/9p2vKq) 
```

Here's a good guide: https://www.chromium.org/developers/design-documents/form-styles-that-chromium-understands/