feat(domain): DomainError::is_transient() for retry classification

crates/domain/src/errors.rs

@@ -20,3 +20,44 @@ pub enum DomainError {
     #[error("Forbidden: {0}")]
     Forbidden(String),
 }
+
+impl DomainError {
+    pub fn is_transient(&self) -> bool {
+        matches!(self, DomainError::InfrastructureError(_))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn infrastructure_error_is_transient() {
+        assert!(DomainError::InfrastructureError("network timeout".into()).is_transient());
+    }
+
+    #[test]
+    fn not_found_is_not_transient() {
+        assert!(!DomainError::NotFound("thing".into()).is_transient());
+    }
+
+    #[test]
+    fn validation_error_is_not_transient() {
+        assert!(!DomainError::ValidationError("bad input".into()).is_transient());
+    }
+
+    #[test]
+    fn unauthorized_is_not_transient() {
+        assert!(!DomainError::Unauthorized("token expired".into()).is_transient());
+    }
+
+    #[test]
+    fn forbidden_is_not_transient() {
+        assert!(!DomainError::Forbidden("no access".into()).is_transient());
+    }
+
+    #[test]
+    fn invalid_rating_is_not_transient() {
+        assert!(!DomainError::InvalidRating { max: 5, given: 9 }.is_transient());
+    }
+}