feat(routing): make client disconnect behavior strategy-scoped

crates/aether-data/contracts/src/repository/usage/metadata_policy.rs

@@ -20,6 +20,14 @@ use super::{
 const UPSTREAM_IS_STREAM_KEY: &str = "upstream_is_stream";
 const PLAN_USAGE_RESERVATION_TOKEN_KEY: &str = "plan_usage_reservation_token";
 const BODY_SIZE_BASIS: &str = "serialized gateway request bodies after normalization";
+pub const CANCELLED_REQUEST_FEE_METADATA_KEY: &str = "cancelled_request_fee";
+
+pub fn cancelled_request_fee_is_billable(metadata: Option<&Value>) -> bool {
+    metadata
+        .and_then(|metadata| metadata.get(CANCELLED_REQUEST_FEE_METADATA_KEY))
+        .and_then(Value::as_bool)
+        .unwrap_or(false)
+}
 
 /// Projects request metadata onto the persistence contract. Unknown fields and malformed values
 /// are discarded instead of being recursively copied into an audit row.
@@ -48,6 +56,7 @@ pub fn sanitize_usage_request_metadata_object(source: &Map<String, Value>) -> Op
         PLAN_USAGE_RESERVATION_DEFERRED_METADATA_KEY,
         "transport_error",
         "is_free_tier",
+        CANCELLED_REQUEST_FEE_METADATA_KEY,
         USAGE_AVAILABLE_METADATA_KEY,
         USAGE_PRICING_AVAILABLE_METADATA_KEY,
     ] {