Fix Retrieve updated document in ReplaceOneAsync method

Core.Blueprint.Mongo/Contracts/ICollectionRepository.cs

@@ -104,11 +104,13 @@ namespace Core.Blueprint.Mongo
         void ReplaceOne(TDocument document);
 
         /// <summary>
-        /// Asynchronously replaces an existing document with a new one.
+        /// Asynchronously replaces an existing document in the collection and returns the updated version.
         /// </summary>
-        /// <param name="document">The document to replace the existing one.</param>
-        /// <returns>A <see cref="Task"/> representing the asynchronous operation.</returns>
-        Task ReplaceOneAsync(TDocument document);
+        /// <param name="document">The document with the updated data. Its _Id is used to locate the existing document.</param>
+        /// <returns>
+        /// The updated document if the replacement was successful; otherwise, <c>null</c> if no matching document was found.
+        /// </returns>
+        Task<TDocument?> ReplaceOneAsync(TDocument document);
 
         /// <summary>
         /// Deletes a single document by the provided filter expression.