Auto Completion: `create`/`update` Attribute Values (Basic)

[steve-r-west]

Let's support auto completion of attribute values.

Acceptance Criteria

1. When you ask to auto complete an attribute if the attribute has type bool we should complete with true or false.
2. When you ask to auto complete an attribute if the attribute has type enum we should recommend completions with the enum values.
3. When you ask to auto complete an attribute if the attribute has type url we should auto complete with "https://".