Function dispatch_collection 

pub async fn dispatch_collection(
    state: State<AppState>,
    authority: Authority,
    path: Path<String>,
    query: Query<HashMap<String, String>>,
    method: Option<Extension<MethodOverride>>,
    body: Option<Json<Value>>,
) -> Response

POST dispatcher for the collection route.

The JavaScript SDK sends every request as a POST and puts the real method in _method. axum matches on the transport method before middleware can rewrite it, so the dispatch happens here, where it is explicit and testable. See body_credentials.