feat(core): Implement DDD, CQRS, and Event Sourcing architecture

- Add project README and Composer configuration with PSR-4 autoloading
- Implement domain layer with AggregateRoot base class for event sourcing
- Create Carrier aggregate with CarrierRegistered domain event
- Add application layer with RegisterCarrierCommand and RegisterCarrierHandler
- Implement infrastructure layer with EventStore interface and CassandraEventStore
- Add CommandBus and Router for request handling and routing
- Create demo test file to showcase carrier registration workflow
- Establish foundation for event-driven architecture with Cassandra persistence

composer.json

@@ -0,0 +1,20 @@
+{
+    "name": "mamad/distributing-carriers",
+    "description": "Distributing Carriers Application with DDD, CQRS, and Event Sourcing",
+    "type": "project",
+    "require": {
+        "php": "^8.0",
+        "ext-cassandra": "*"
+    },
+    "autoload": {
+        "psr-4": {
+            "DistributingCarriers\\": "src/"
+        }
+    },
+    "authors": [
+        {
+            "name": "Mamad",
+            "email": "mamad@example.com"
+        }
+    ]
+}