added tests for partitioned collections

MongoDbGenericRepository/Models/IDocument.cs

@@ -2,11 +2,25 @@
 
 namespace MongoDbGenericRepository.Models
 {
+    /// <summary>
+    /// This class represents a basic document that can be stored in MongoDb.
+    /// Your document must implement this class in order for the MongoDbRepository to handle them.
+    /// </summary>
     public interface IDocument
     {
         DateTime AddedAtUtc { get; set; }
         Guid Id { get; set; }
-        string PartitionKey { get; set; }
         int Version { get; set; }
     }
+
+    /// <summary>
+    /// This class represents a document that can be inserted in a collection that can be partitioned.
+    /// The partition key allows for the creation of different collections having the same document schema.
+    /// This can be useful if you are planning to build a Software as a Service (SaaS) Platform, or if you want to reduce indexing.
+    /// You could for example insert Logs in different collections based on the week and year they where created, or their Log category/source.
+    /// </summary>
+    public interface IPartitionedDocument : IDocument
+    {
+        string PartitionKey { get; set; }
+    }
 }