Function
insert-header-pending
Sets a response header to the given value on a pending response.
This will discard any previous values for the given header name, including any
pending header changes previously queued via other insert-header-pending or
append-header-pending calls for the same header name.
The target argument controls under which conditions this header is applied.
insert-header-pending: func(pending: borrow<pending-response>, name: string, value: list<u8>, target: pending-response-kind) -> result<_, error>;