feat: Add Pain.007.001.03 Builder and corresponding unit tests for ISO 20022 message construction

- Implemented Pain00700103Builder for constructing and serializing ISO 20022 pain.007.001.03 messages (Customer Payment Reversal V03).
- Added builder registration in MessageBuilderFactory for MessageType.Pain00700103.
- Comprehensive unit tests created for Pain00700103Builder covering all functionalities including group header, original group information, payment instructions, and transaction reversals.
- Updated changelog to reflect the addition of Pain.007.001.03 Builder support.

Author: cleilson pereira

Iso20022Library.Application/Builders/MessageBuilderFactory.cs

@@ -41,7 +41,8 @@ public class MessageBuilderFactory
         { MessageType.Pain00200107, () => new Pain.Pain00200107Builder() },
         { MessageType.Pain00200108, () => new Pain.Pain00200108Builder() },
         { MessageType.Pain00200109, () => new Pain.Pain00200109Builder() },
-        { MessageType.Pain00200110, () => new Pain.Pain00200110Builder() }
+        { MessageType.Pain00200110, () => new Pain.Pain00200110Builder() },
+        { MessageType.Pain00700103, () => new Pain00700103Builder() }
     };
 
     /// <summary>