Replace JsInstance checkout/return with worker and FIFO queue

Author: joshua-spacetime

crates/client-api/src/routes/database.rs

@@ -98,6 +98,7 @@ fn map_reducer_error(e: ReducerCallError, reducer: &str) -> (StatusCode, String)
             log::debug!("Attempt to call non-existent reducer {reducer}");
             StatusCode::NOT_FOUND
         }
+        ReducerCallError::WorkerError(_) => StatusCode::INTERNAL_SERVER_ERROR,
         ReducerCallError::LifecycleReducer(lifecycle) => {
             log::debug!("Attempt to call {lifecycle:?} lifecycle reducer {reducer}");
             StatusCode::BAD_REQUEST