Add cleanup in DocumentUrl tables when the content key changes.

[KevinJump]

Workaround for umbraco/Umbraco-CMS#21131.

When a content item's Key changes during an import - Umbraco throws an ForeignKey exception because of the bindings to the umbracoDocumentUrl table.

This PR checks on key changes, and removes entries from that table (via the repository). - so the conflict doesn't happen.

On Save Umbraco puts new entries in the table with the new Key so this "should" be ok.

[Copilot]

Pull request overview

This PR addresses a foreign key constraint violation that occurs when a content item's Key changes during import. The fix involves cleaning up entries in the umbracoDocumentUrl table before the key change is applied, preventing the constraint violation. Umbraco will repopulate the table with the new Key on save.

Key Changes:

• Introduced ISyncDocumentUrlCleaner interface and SyncDocumentUrlCleaner implementation to handle DocumentUrl table cleanup
• Added OnKeyChange virtual method in ContentSerializerBase to allow subclasses to respond to key changes
• Integrated URL cleaning into ContentSerializer when key changes are detected

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
uSync.Core/Documents/ISyncDocumentUrlCleaner.cs	New interface for document URL cleanup functionality
uSync.Core/Documents/SyncDocumentUrlCleaner.cs	Implementation that deletes DocumentUrl entries by document key using repository
uSync.Core/uSyncCoreBuilderExtensions.cs	Registers the URL cleaner as a singleton service
uSync.Core/Serialization/Serializers/ContentSerializerBase.cs	Adds virtual OnKeyChange method called when a content key changes
uSync.Core/Serialization/Serializers/ContentSerializer.cs	Overrides OnKeyChange to invoke URL cleaner and adds it as a dependency
uSync.Core/Serialization/Serializers/ContentTemplateSerializer.cs	Updates constructor to accept and pass the URL cleaner to base class

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[KevinJump]

Warning

(Breaking - changes the Constructor for the ContentSerializer class)