error: Cannot return tuples with more than 17 elements
  --> tests/debug_handler/fail/output_tuple_too_many.rs:4:20
   |
4  |   async fn handler() -> (
   |  ____________________^
5  | |     axum::http::StatusCode,
6  | |     AppendHeaders<[(axum::http::HeaderName, &'static str); 1]>,
7  | |     AppendHeaders<[(axum::http::HeaderName, &'static str); 1]>,
...  |
23 | |     axum::http::StatusCode,
24 | | ) {
   | |_^