init domain

crates/domain/src/errors.rs

@@ -0,0 +1,16 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub enum DomainError {
+    #[error("Rating must be between 0 and {max}, but received {given}")]
+    InvalidRating { max: u8, given: u8 },
+
+    #[error("Entity not found: {0}")]
+    NotFound(String),
+
+    #[error("Business rule violation: {0}")]
+    ValidationError(String),
+
+    #[error("Infrastructure failure: {0}")]
+    InfrastructureError(String),
+}