🧑‍💻(admin) add selftest views mechanism

[qbey]

Purpose

This allows to define views available in /admin/selftest/ like an email sender testing view for instance.

I'm still not sure about this...

Proposal

• provide base selftest views
• provider an index view for selftests
• add an example selftest : email
• add tests

[Copilot]

Pull Request Overview

This PR introduces a mechanism to register and serve selftest views in the Django admin, allowing the addition of testing views (e.g. an email sender test view) under the /admin/selftest/ URL.

• Introduces a base selftest view (BaseSelftestAdminPageView) and a dedicated index view (IndexSelftestAdminPageView).
• Adds an example email selftest view (EmailSelftestAdminPageView) with GET and POST handlers for sending test emails.
• Implements a registry (ViewRegistry) to automatically discover and register selftest views and extends the admin site URLs accordingly.

Reviewed Changes

Copilot reviewed 3 out of 6 changed files in this pull request and generated no comments.

File	Description
src/backend/admin/views.py	Adds base, index, and email selftest views with GET and POST handling.
src/backend/admin/sites.py	Extends the admin site URLs to include registered selftest views.
src/backend/admin/registry.py	Implements a registry to auto-discover and register custom selftest views.

Files not reviewed (3)

• src/backend/admin/templates/selftest/base.html: Language not supported
• src/backend/admin/templates/selftest/email.html: Language not supported
• src/backend/admin/templates/selftest/index.html: Language not supported

Comments suppressed due to low confidence (2)

src/backend/admin/registry.py:42

• [nitpick] Consider handling edge cases where the subclass name matches exactly 'SelftestAdminPageView', which may result in an empty name. A more robust naming strategy would prevent potential routing issues.

base_name = name.replace("SelftestAdminPageView", "").lower()

src/backend/admin/views.py:67

• The POST method in EmailSelftestAdminPageView does not have test coverage. Please add tests to ensure the email sending behavior and error handling work as expected.

def post(self, request, *args, **kwargs):