feat(mfa): replace trench based API endpoints, views and forms with allauth implementation DEV-749

[Guitlle]

🗒️ Checklist

1. run linter locally
2. update developer docs (API, README, inline, etc.), if any
3. for user-facing doc changes create a Zulip thread at #Support Docs Updates, if any
4. draft PR with a title <type>(<scope>)<!>: <title> DEV-1234
5. assign yourself, tag PR: at least Front end and/or Back end or workflow
6. fill in the template below and delete template comments
7. review thyself: read the diff and repro the preview as written
8. open PR & confirm that CI passes & request reviewers, if needed
9. delete this section before merging

Summary

Migrate MFA features from Trench to Django Allauth for better integration, maintainability.

Description

This update replaces all Trench-based multi-factor authentication (MFA) endpoints, views, and forms with a new implementation powered by Django Allauth. The change ensures tighter integration with the existing authentication system, simplifies configuration, and improves long-term maintainability.

💭 Notes

The MFA endpoints were changed to use the allauth MFA feature and removing trench. This covers these endpoints that are used in the frontend:

• /api/v2/auth/str:method/activate/
• /api/v2/auth/str:method/activate/confirm/
• /api/v2/auth/str:method/codes/regenerate/
• /api/v2/auth/str:method/deactivate/
• /api/v2/auth/mfa/user-active-methods/

These are now based on the Authenticator model, which can handle TOTP codes and recovery codes.

👀 Preview steps

These endpoints are covered in unit tests, so no need to test. However we could test the following sequence to validate it's working ok:

1. Log into your dev env
2. Go to account settings
3. Go to security
4. Enable MFA and you can use pyotp to generate codes, or you can use an auth app in your phone
5. Scan the QR code or copy the manual key, use pyotp:

>>> import pyotp
>>> key = '*****'
>>> totp = pyotp.TOTP(key)
>>> totp.now()

123456

6. Enter the generated code and it should now show you the recovery codes. Download the file, and click the blue button
7. You should see that there are two options now, reconfigure MFA and regenerate codes
8. Test each one of these, it should allow you to follow the steps with no error messages in the KPI container logs or in the frontend app. Use pyotp to generate new codes, as shown above.

[noliveleger]

LGTM