Refactor Token model

[Radiokot]

Purpose

Refactor the model to make working with it easier when implementing CIS-2 notifications.

Changes

• Get rid of useless fields
• Simplify construction

Checklist

• [x] My code follows the style of this project.
• [x] The code compiles without warnings.
• [x] I have performed a self-review of the changes.
• [x] I have documented my code, in particular the intent of the hard-to-understand areas.