BIZ-3 Add keys to ChoiceSets

[natm]

Solves #189

https://linear.app/netboxlabs/issue/BIZ-3/

[cruse1977]

Testing:

Std - without FIELD_CHOICES:

With FIELD_CHOICES as:

FIELD_CHOICES = {
        'netbox_bgp.Session.status': [
                ('left', 'Left', 'green'),
                ('right', 'Right', 'blue'),
        ]
}