Create a new model for snapshot

[susilnem]

We need to create a new model called LocalUnitChangeRequest to track changes to the LocalUnit data.

The fields for the LocalUnitChangeRequest model should include:

1. previous_data:

   • Type: JsonField (used to store the previous state of the fields)

2. status:

   • Options:
     • PENDING
     • APPROVED
     • REVERT

3. current_validator:

   • Type: Enum
   • Options:
     • LOCAL
     • REGIONAL
     • GLOBAL

4. triggered_by:

   • Field to record who triggered the change request.

5. triggered_at:

   • Timestamp for when the change was triggered.

6. updated_by:

   • Field to record who made updates to the request.

7. updated_at:

   • Timestamp for when the request was last updated.

8. rejected_data:

   • Type: JsonField (stores data that was rejected during the request process)

9. rejected_reason:

   • Field to describe why the request was rejected.

This model will help track and manage changes to LocalUnit data through different validation stages and actions.