Pull Request Template

What does this PR do?

This PR introduces a microservice-based architecture that includes a polling-publisher and a subscriber-service communicating via Apache Kafka. It demonstrates an in-memory data flow mechanism using Kafka topics.

The PR includes:

Kafka producer REST endpoint for sending messages
Kafka consumer that listens automatically and processes messages
Spring Boot configuration for both microservices
Initial testing and local setup for message flow validation

Fixes #2673

Type of change

[x] New feature (non-breaking change)
[x] Documentation update

How has this been tested?

Manually tested Kafka message publishing via /send endpoint
Verified automatic listening and processing in subscriber microservice
Logs and terminal output confirm end-to-end communication

Additional context

Both microservices are designed for local Kafka communication using port 9092. Make sure the Kafka broker is running before testing

Apr 06 '25 12:04 quantdevv

PR Summary

This PR introduces a microservice-based architecture with a polling publisher and subscriber service communicating via Apache Kafka. It demonstrates an in-memory data flow mechanism using Kafka topics, including a Kafka producer REST endpoint, a Kafka consumer, Spring Boot configuration for both microservices, and initial testing.

Changes

File	Summary
`clean-architecture/src/main/java/com/iluwatar/cleanarchitecture/App.java`	Updated license header in the `App.java` file.
`clean-architecture/src/main/java/com/iluwatar/cleanarchitecture/Cart.java`	Updated license header in the `Cart.java` file.
`clean-architecture/src/main/java/com/iluwatar/cleanarchitecture/CartController.java`	Updated license header in the `CartController.java` file.
`clean-architecture/src/main/java/com/iluwatar/cleanarchitecture/CartRepository.java`	Updated license header in the `CartRepository.java` file.
`clean-architecture/src/main/java/com/iluwatar/cleanarchitecture/InMemoryCartRepository.java`	Updated license header in the `InMemoryCartRepository.java` file.
`clean-architecture/src/main/java/com/iluwatar/cleanarchitecture/InMemoryOrderRepository.java`	Updated license header in the `InMemoryOrderRepository.java` file.
`clean-architecture/src/main/java/com/iluwatar/cleanarchitecture/InMemoryProductRepository.java`	Updated license header in the `InMemoryProductRepository.java` file.
`clean-architecture/src/main/java/com/iluwatar/cleanarchitecture/Order.java`	Updated license header in the `Order.java` file.
`clean-architecture/src/main/java/com/iluwatar/cleanarchitecture/OrderController.java`	Updated license header in the `OrderController.java` file.
`clean-architecture/src/main/java/com/iluwatar/cleanarchitecture/OrderRepository.java`	Updated license header in the `OrderRepository.java` file.
`clean-architecture/src/main/java/com/iluwatar/cleanarchitecture/Product.java`	Updated license header in the `Product.java` file.
`clean-architecture/src/main/java/com/iluwatar/cleanarchitecture/ProductRepository.java`	Updated license header in the `ProductRepository.java` file.
`clean-architecture/src/main/java/com/iluwatar/cleanarchitecture/ShoppingCartService.java`	Updated license header in the `ShoppingCartService.java` file.
`clean-architecture/src/main/java/com/iluwatar/cleanarchitecture/package-info.java`	Updated license header in the `package-info.java` file.
`clean-architecture/src/test/java/com/iluwatar/cleanarchitecture/AppTest.java`	Updated license header in the `AppTest.java` file.
`clean-architecture/src/test/java/com/iluwatar/cleanarchitecture/CartControllerTest.java`	Updated license header in the `CartControllerTest.java` file.
`polling-publisher/README.md`	New file: README for the polling publisher project, describing the project structure, tech stack, and setup instructions.
`polling-publisher/etc/polling-publisher.urm.puml`	New file: Empty plantuml file for the polling publisher.
`polling-publisher/polling-service/README.md`	New file: README for the polling service, explaining its functionality and structure.
`polling-publisher/polling-service/etc/polling-service.urm.puml`	New file: Empty plantuml file for the polling service.
`polling-publisher/polling-service/pom.xml`	New file: POM file for the polling service module, defining dependencies and build configurations.
`polling-publisher/polling-service/src/main/java/com/iluwatar/polling/App.java`	New file: Main application class for the polling service, using Spring Boot.
`polling-publisher/polling-service/src/main/java/com/iluwatar/polling/DataRepository.java`	New file: Repository class for managing in-memory data, using a HashMap.
`polling-publisher/polling-service/src/main/java/com/iluwatar/polling/DataSourceService.java`	New file: Service class for interacting with the data source, adding, retrieving, and removing data.
`polling-publisher/polling-service/src/main/java/com/iluwatar/polling/KafkaProducer.java`	New file: Producer class for sending messages to Kafka, using Spring Kafka.
`polling-publisher/polling-service/src/main/java/com/iluwatar/polling/PollingController.java`	New file: Controller class for handling REST endpoints, including a health check and a message sending endpoint.
`polling-publisher/polling-service/src/main/java/com/iluwatar/polling/PollingScheduler.java`	New file: Scheduler class for periodically polling the data source and publishing updates to Kafka.
`polling-publisher/polling-service/src/main/resources/application.yml`	New file: Configuration file for the polling service, specifying server port and Kafka connection details.
`polling-publisher/polling-service/src/test/java/com/iluwatar/polling/AppTest.java`	New file: Test class for the polling service application, verifying the main method execution.
`polling-publisher/polling-service/src/test/java/com/iluwatar/polling/DataRepositoryTest.java`	New file: Test class for the DataRepository, covering save, findById, delete, and findAll methods.