docs: add service layer architecture diagram

Author: iluwatar

Diff for: service-layer/README.md

@@ -36,6 +36,11 @@ Wikipedia says
 
 > Service layer is an architectural pattern, applied within the service-orientation design paradigm, which aims to organize the services, within a service inventory, into a set of logical layers. Services that are categorized into a particular layer share functionality. This helps to reduce the conceptual overhead related to managing the service inventory, as the services belonging to the same layer address a smaller set of activities.
 
+Architecture diagram
+
+![Service Layer Architecture Diagram](./etc/service-layer-architecture-diagram.png)
+
+
 ## Programmatic Example of Service Layer Pattern in Java
 
 Our Java implementation uses the Service Layer pattern to streamline interactions between data access objects (DAOs) and the business logic, ensuring a clean separation of concerns.