Register no-op implementation of IMemberPartialViewCacheInvalidator in headless setups

[AndyButland]

Prerequisites

• I have added steps to test this contribution in the description below

Resolves: #19661

Description

As the linked issue discusses, when we don't have a call to .AddWebsite() in Program.cs, the IMemberPartialViewCacheInvalidator has no registered implementation, which causes an error when logging in.

This PR registers a no-op implementation of this interface that'll be overridden by the primary implementation if .AddWebsite() is used.

Testing

Setup Program.cs like the following, so there's no front-end website but you should be able log into the backoffice.

Verify that you can't before this PR is applied but you can after.

Revert to the standard setup for Umbraco with the front-end rendering, put a breaking point in MemberPartialViewCacheInvalidator.ClearPartialViewCacheItems and verify that the primary implementation is called when saving a member in the backoffice.

[Copilot]

Pull Request Overview

This PR ensures that a default no-op implementation of IMemberPartialViewCacheInvalidator is registered in headless (no-website) setups to prevent missing-service errors while allowing the real implementation to override it when .AddWebsite() is used.

• Registers NoopMemberPartialViewCacheInvalidator in UmbracoBuilder.AddCoreServices()
• Adds a new internal no-op class under Cache.PartialViewCacheInvalidators
• Removes a duplicate using directive

Reviewed Changes

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

File	Description
src/Umbraco.Core/DependencyInjection/UmbracoBuilder.cs	Registers default no-op invalidator for headless setups
src/Umbraco.Core/Cache/PartialViewCacheInvalidators/NoopMemberPartialViewCacheInvalidator.cs	Introduces an internal no-op implementation of the cache invalidator

Comments suppressed due to low confidence (2)

src/Umbraco.Core/DependencyInjection/UmbracoBuilder.cs:349

• Consider adding a unit or integration test to verify that in a headless setup (without .AddWebsite()), the DI container resolves IMemberPartialViewCacheInvalidator to the no-op implementation and does not throw when logging in.

            Services.AddUnique<IMemberPartialViewCacheInvalidator, NoopMemberPartialViewCacheInvalidator>();

src/Umbraco.Core/Cache/PartialViewCacheInvalidators/NoopMemberPartialViewCacheInvalidator.cs:3

• [nitpick] It may help maintainability to add a brief XML doc comment on this class explaining its purpose and override behavior when .AddWebsite() is used.

internal class NoopMemberPartialViewCacheInvalidator : IMemberPartialViewCacheInvalidator