Add models for some more minor Observation attributes

[JWCook]

Remaining attributes that are still dicts:

• [ ] quality_metrics
• [ ] faves
• [ ] votes
• [ ] sounds

quality_metrics Example:

{
    'user_id': 226624,
    'metric': 'wild',
    'id': 378812,
    'agree': False,
    'user': {
        'id': 226624,
        'login': 'some_username',
        ...,
    }
}