Added comments for no-op partial view cache invalidator.

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

@@ -1,7 +1,15 @@
 namespace Umbraco.Cms.Core.Cache.PartialViewCacheInvalidators;
 
+/// <summary>
+/// Provides a no-operation implementation of <see cref="IMemberPartialViewCacheInvalidator"/>.
+/// </summary>
+/// <remarks>
+/// The default implementation is added in Umbraco.Web.Website, but we need this to ensure we have a service
+/// registered for this interface even in headless setups).
+/// </remarks>
 internal class NoopMemberPartialViewCacheInvalidator : IMemberPartialViewCacheInvalidator
 {
+    /// <inheritdoc/>
     public void ClearPartialViewCacheItems(IEnumerable<int> memberIds)
     {
         // No operation performed, this is a no-op implementation.