Fix for collection resource_list_items with deleted contributor

[stuzart]

• fix for Collection list item doesn't handle deleted contributors #2212

[Copilot]

Pull Request Overview

This PR adds support for a deleted_contributor field on file_templates and placeholders, updates schema/migrations, and adjusts tests and views to handle deleted contributors in collection list items.

• Introduced deleted_contributor columns for new resource types and bumped schema version
• Extended unit and integration tests to cover deleted‐contributor behavior
• Updated collection item view to compact nil maintainers and use the dynamic “creators” label

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
test/unit/asset_test.rb	Added new asset types (:placeholder, :file_template, etc.) to deleted_contributor unit test
test/integration/index_pages_test.rb	Added integration test for list items when contributor is deleted (spelling needs correction)
test/functional/collections_controller_test.rb	Updated controller tests for deleted contributors and creator labels (assert usage and labels need fixes)
db/schema.rb	Bumped schema version and added deleted_contributor to tables
db/migrate/20250610150119_add_deleted_contributor_to_placeholder.rb	Migration to add deleted_contributor to placeholders
db/migrate/20250610150132_add_deleted_contributor_to_file_template.rb	Migration to add deleted_contributor to file_templates
app/views/collections/_resource_list_item.html.erb	Compact nil maintainers and switch to human_attribute_name('creators') for the label