`check_entry_fields` returned `Result<(), Response>`, which trips
`clippy::result_large_err` under CI's `-D warnings`: an axum `Response` is 128
bytes and it was riding in the `Err` variant.
`Option<Response>` is the shape this always wanted. There is no error value to
propagate here — the "error" IS the response the handler sends back — so `None`
means "the payload may proceed" and `Some(r)` is the refusal to return. The call
sites read the same, one word different.
Caught by CI, not by me: I ran `cargo check` and not `cargo clippy -D warnings`.
enricobuehler
0d94ef0dbe