Can I 'POST' Raw Data to a Web API?

The http class looks to have options for encoding the body as json or form. Is there a way to post as raw?

I can specify this in Postman, but without seeing a way to do this from Drafts, all I have so far is being able to get JSON through to the other end, but the entire JSON string is the payload, and I need to send a string that isn’t JSON.

I can split by OS, shelling out to use curl on the Mac, and use a Shortcut on i*OS (setting the body as a file and passing it text for a Get Contents of action seems to work), but I’m thinking that it would be more efficient, at least in terms of simple maintenance, if I can utilise just the native Drafts functionality instead.