fix: Use Django admin autocomplete widgets in alias plugin form

[fsbraun]

Summary by Sourcery

Replace the alias plugin's custom Select2 endpoints with Django admin autocomplete integration while preserving context-sensitive choices and compatibility warnings.

New Features:

• Use Django admin autocomplete widgets for alias plugin category and alias selection with site, category, and language-aware filtering.

Bug Fixes:

• Ensure autocomplete choices are limited to valid aliases and categories for the current plugin context.

Enhancements:

• Deprecate the legacy alias and category Select2 endpoints in favor of Django admin's autocomplete endpoint.

Tests:

• Add coverage for widget configuration, autocomplete permissions, filtering, ordering, language, site, and deprecation warnings.

Related resources

• fixes BUG: forms use outdated CMS select2 widget #361
• #...

Checklist

• I have added or modified the tests when changing logic
• I have followed the conventional commits guidelines to add meaningful information into the changelog
• I have read the contribution guidelines

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Reviewer's Guide

The PR migrates the alias plugin form from custom Select2 endpoints to Django admin’s autocomplete widgets and endpoint, adding server-side contextual filtering and client-side site/category parameters while preserving legacy endpoints with deprecation warnings and expanding coverage.

Sequence diagram for contextual alias plugin autocomplete

sequenceDiagram
    participant Form as Alias plugin form
    participant JS as alias_plugin.js
    participant Admin as Django admin:autocomplete
    participant CategoryAdmin
    participant AliasAdmin
    participant DB as Database

    Form->>JS: djangocmsAliasSelect2()
    JS->>Admin: autocomplete request with site, category, and search term
    alt Category field
        Admin->>CategoryAdmin: get_search_results(request, queryset, search_term)
        CategoryAdmin->>DB: Filter categories with aliases and selected site
        DB-->>CategoryAdmin: Matching categories
        CategoryAdmin-->>Admin: Ordered category results
    else Alias field
        Admin->>AliasAdmin: get_search_results(request, queryset, search_term)
        AliasAdmin->>DB: Filter language, category, and selected site
        DB-->>AliasAdmin: Matching aliases
        AliasAdmin-->>Admin: Ordered alias results
    end
    Admin-->>JS: JSON autocomplete results
    JS-->>Form: Update Select2 choices

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File-Level Changes

Change	Details	Files
Replace custom Select2 endpoints and widgets with Django admin autocomplete integration.	Build category and alias fields with AutocompleteSelect and preserve form placeholders. Customize admin search results for language, category, site, alias availability, and stable ordering. Add client-side autocomplete initialization that forwards selected site and category filters.	djangocms_alias/admin.py djangocms_alias/forms.py djangocms_alias/static/djangocms_alias/js/alias_plugin.js djangocms_alias/static/djangocms_alias/css/autocomplete.css
Retain legacy autocomplete endpoints as deprecated compatibility APIs.	Emit DeprecationWarning from both legacy Select2 views. Document migration to admin:autocomplete.	djangocms_alias/views.py
Validate widget configuration, autocomplete filtering, ordering, permissions, and deprecation behavior.	Test admin autocomplete widget attributes and media ordering. Test language, search-term, category, site, and category-availability filtering. Test staff access requirements and legacy endpoint warnings.	tests/test_cms_plugins.py tests/test_views.py
Remove obsolete custom Select2 initialization and endpoint-specific form wiring.	Delete the legacy create.js asset. Remove custom endpoint URL construction and old widget rendering logic.	djangocms_alias/static/djangocms_alias/js/create.js djangocms_alias/forms.py

Assessment against linked issues

Issue	Objective	Addressed	Explanation
#361	Replace the alias plugin form's outdated custom Select2 widgets with Django admin's autocomplete widgets, using Django admin's jQuery and Select2 assets.	✅
#361	Ensure category and alias autocomplete requests provide the plugin's site/category context and return appropriately filtered, language-aware choices.	✅
#361	Retain compatibility for the previous Select2 endpoints while directing new integrations to the Django admin autocomplete endpoint.	✅

Possibly linked issues

• BUG: forms use outdated CMS select2 widget #361: The PR enables admin autocomplete alias selection, directly resolving the changelist form’s missing Alias workflow.

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Sourcery assessment

Approved.