refactor: restructure domain crate by bounded context

crates/domain/src/common/ports.rs

@@ -0,0 +1,8 @@
+use async_trait::async_trait;
+use crate::common::errors::DomainError;
+use crate::common::events::DomainEvent;
+
+#[async_trait]
+pub trait EventPublisher: Send + Sync {
+    async fn publish(&self, event: DomainEvent) -> Result<(), DomainError>;
+}