Added docs around IMemberPartialViewCacheInvalidator

13/umbraco-cms/reference/cache/imemberpartialviewcacheinvalidator.md

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+# Partial view cache refresher for members
+
+This section describes the `IMemberPartialViewCacheInvalidator` interface, what it's default implementation does and how to customize it.
+
+## What is an IMemberPartialViewCacheInvalidator?
+
+This interface is used to isolate the logic that invalidates parts of the partial view cache when a member is updated.
+
+## Why do we need to partially invalidate the partial view cache?
+
+Razor templates showing data retrieved from a member object can be cached as partial views via:
+
+
+## Where is it used?
+
+This interface is called from the member cache refresher (`MemberCacheRefresher`), which is invoked every time a member is updated.
+
+## Details of the default implementation
+
+Razor template partials are cached through a call to `Html.CachedPartialAsync` with `cacheByMember` set to `true`. This will append the ID of the currently logged-in member with a marker to the partial view cache key.  For example, `-m1015-`. 
+
+When the `ClearPartialViewCacheItems` method is called it will clear all cache items that match the marker for the updated members.
+
+If no member is logged in during caching, items with an empty member marker (for example, `-m-`) are also cleared.
+
+## Customizing the implementation
+
+You can replace the default implementation by removing it and registering your own in a composer.
+
+```csharp
+public class ReplaceMemberCacheInvalidatorComposer : IComposer
+{
+    public void Compose(IUmbracoBuilder builder)
+    {
+        builder.Services.AddUnique<IMemberPartialViewCacheInvalidator, MyCustomMemberPartialViewCacheInvalidator>();
+    }
+}
+```

16/umbraco-cms/reference/cache/imemberpartialviewcacheinvalidator.md

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+# Partial view cache refresher for members
+
+This section describes the `IMemberPartialViewCacheInvalidator` interface, what it's default implementation does and how to customize it.
+
+## What is an IMemberPartialViewCacheInvalidator?
+
+This interface is used to isolate the logic that invalidates parts of the partial view cache when a member is updated.
+
+## Why do we need to partially invalidate the partial view cache?
+
+Razor templates may show data that is retrieved from a member object. Those templates might be cached by using the partial caching mechanism (for example, `@await Html.CachedPartialAsync("member",Model,TimeSpan.FromDays(1), cacheByMember:true)`). When a member is updated, these cached partials must be invalidated to ensure updated data is shown.
+
+## Where is it used?
+
+This interface is called from the member cache refresher (`MemberCacheRefresher`), which is invoked every time a member is updated.
+
+## Details of the default implementation
+
+Razor template partials are cached through a call to `Html.CachedPartialAsync` with `cacheByMember` set to `true`. This will append the ID of the currently logged-in member with a marker to the partial view cache key.  For example, `-m1015-`. 
+
+When the `ClearPartialViewCacheItems` method is called, it will clear all cache items that match the marker for the updated members.
+
+If no member is logged in during caching, items with an empty member marker (for example, `-m-`) are also cleared.
+
+## Customizing the implementation
+
+You can replace the default implementation by removing it and registering your own in a composer.
+
+```csharp
+public class ReplaceMemberCacheInvalidatorComposer : IComposer
+{
+    public void Compose(IUmbracoBuilder builder)
+    {
+        builder.Services.AddUnique<IMemberPartialViewCacheInvalidator, MyCustomMemberPartialViewCacheInvalidator>();
+    }
+}
+```