Method input_response_handler

Handler for `/input_response/{runner_id}/{callback_id}`. Called by the executor when a form is submitted. The runner_id check guards against stale URLs that name a different pod (e.g. submission arriving after this pod was rescheduled to the same IP).

(
        axum::extract::State(runner): axum::extract::State<Self>,
        axum::extract::Path((runner_id, callback_id)): axum::extract::Path<(String, String)>,
        Json(input): Json<serde_json::