Update the user models to use declarative models

[ZechCodes]

Refer to the Using Declarative Models wiki.

Go through the users.py in dippy/core/api/models and do the following

1. As the very first line add from __future__ import annotations as _
2. Remove the import for the attrs module
3. Import Model from dippy.core.model.models
4. Remove all @attrs lines and update each class with to inherit Model
5. Replace any attrib(...) assignments

• You will need to import Field from dippy.core.models.fields
• Replace attrib with Field

6. Replace any json_arg(...) assignments the same way as attrib assignments

⚠️ Please make each file changed its own commit. ⚠️

[burning-eggs]

assign me :))))

[burning-eggs]

This has been implemented in PR #24