fix: stop Route admin change page from timing out

[chrisdoehring]

Problem

Requesting the Django admin change page for a Route (e.g. /admin/integrations/route/<id>/change/) times out in production.

Root cause

The change page renders RouteProviderInline and RouteDestinationInline. Each inline renders a <select> of every Integration — for every existing row and every extra form. Integration.__str__ is f"{self.owner.name} - {self.name} - {self.type.name}", and neither owner nor type is select_related, so building each dropdown fires N+1 queries. The total cost scales with the number of integrations, which is large in production → timeout.

Quantified with the new regression test: rendering the page went from 460 → 4,259 queries after adding just 100 integrations (~38 queries per integration).

This is distinct from the changelist COUNT(*) issue fixed in #418 — this is the single-object change view and its inlines.

Fix

Add autocomplete_fields = ("integration",) to both inlines. The FK now renders as an AJAX autocomplete box (backed by IntegrationAdmin's existing search_fields) instead of a full-table dropdown, so no Integration options are pre-rendered and there is no N+1.

Testing

• New integrations/tests/test_admin.py renders the change page, adds 100 integrations, and asserts the query count stays flat (delta ≤ 10). Fails before the fix, passes after.
• manage.py check passes (confirms the autocomplete_fields config is valid and won't break admin startup).

Note for reviewers

Staff users need view permission on Integration for the autocomplete results to populate (standard Django autocomplete behavior). Superusers and typical admin roles already have it.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR addresses production timeouts when rendering the Django admin Route change page by preventing the inlines from pre-rendering a full-table <select> of all Integration rows (which previously triggered N+1 queries via Integration.__str__).

Changes:

• Switched RouteProviderInline and RouteDestinationInline to use autocomplete_fields = ("integration",) to avoid rendering all Integration options.
• Added a regression test that asserts the Route change page query count does not grow materially after adding 100 Integration rows.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
cdip_admin/integrations/admin.py	Uses autocomplete_fields on Route-related inlines to avoid full-table dropdown rendering and N+1 queries.
cdip_admin/integrations/tests/test_admin.py	Adds a query-count regression test ensuring Route change page rendering stays flat as integrations increase.

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