[Docs] Add AK1008 documentation (#7504)

Author: Arkatufus

docs/articles/debugging/rules/AK1008.md

@@ -0,0 +1,58 @@
+---
+uid: AK1008
+title: Akka.Analyzers Rule AK1008 - "Creating actors using `ActorSystem.ActorOf()` inside an actor"
+---
+
+# AK1008 - Warning
+
+Creating actors using `Context.System.ActorOf()` inside an actor is discouraged because the resulting actor would not be the child of this actor but the "/user" guardian actor itself. Please use `Context.ActorOf()` if your intention is to create a child actor of this actor.
+
+## Cause
+
+Creating an `IActorRef`  Using `Context.System.ActorOf()` or `Context.System.ActorOf<T>()` inside a class that inherits `ReceiveActor` or `UntypedActor` would create an actor as a child the "/user" guardian actor instead of a child actor under the invoking actor.
+
+You can suppress this warning message if you specifically intended to create a new actor under the "/user" guardian actor.
+
+Example:
+
+```csharp
+using System;
+using Akka.Actor;
+
+public sealed class FirstActor : ReceiveActor
+{
+    public FirstActor()
+    {
+        Context.System.ActorOf<MyActor>("newActor");
+    }
+}
+
+public sealed class MyActor : ReceiveActor
+{
+}
+```
+
+![Actor created in wrong path](/images/debugging/rules/AK1008-Wrong-path.png)
+
+## Resolution
+
+Use `Context.ActorOf()` or `Context.ActorOf<T>()` method instead to create a new child actor:
+
+```csharp
+using System;
+using Akka.Actor;
+
+public sealed class FirstActor : ReceiveActor
+{
+    public FirstActor()
+    {
+        Context.ActorOf<MyActor>("newActor");
+    }
+}
+
+public sealed class MyActor : ReceiveActor
+{
+}
+```
+
+![Actor created as child actor](/images/debugging/rules/AK1008-Right-path.png)

docs/articles/debugging/rules/toc.yml

@@ -14,6 +14,8 @@
   href: AK1006.md
 - name: AK1007
   href: AK1007.md
+- name: AK1008
+  href: AK1008.md
 - name: AK2000
   href: AK2000.md
 - name: AK2001