Add Documentation attributes

part of https://github.com/oqtane/oqtane.framework/issues/570

Oqtane.Shared/Documentation/WorkInProgressApi.cs

@@ -0,0 +1,18 @@
+using System;
+
+namespace Oqtane.Documentation
+{
+    /// <summary>
+    /// This attribute marks APIs to be publicly documented with a clear warning that it's work in progress.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.All, AllowMultiple = true, Inherited = false)]
+    [PublicApi]
+    public class WorkInProgressApi: Attribute
+    {
+        /// <summary>
+        /// The `[WorkInProgressApi(some-comment)]` attributes must always have a comment why they are WIP.
+        /// </summary>
+        /// <param name="comment">Reason why it's WIP, required</param>
+        public WorkInProgressApi(string comment) { }
+    }
+}