Transmission custom-api or widget?

### Description

I'm trying to integrate Transmission into my dashboard.

To do that, I first need to make a POST request to retrieve the `X-Transmission-Session-Id` from the response headers. Then, I need to make a second request using that session ID in the headers to get the actual JSON response.

I tried using `custom-api`, but it doesn't seem possible since subrequests are executed at the same time as the main request, which prevents passing the session ID between them.

I'm not sure what's easier on your side — either allowing headers to be passed from the main request to subrequests, or maybe creating a dedicated widget for Transmission?

Let me know what you think or if there's another way I could approach this. Thanks!