Get sermon upload working with API routes

[readeral]

Currently sermon upload implementation is built around a serverless function on AWS. It's not scaleable and is currently broken, so ideally we're doing it via API routes.

I've tried to get this going, but it's not really working for me. There is existing code in both this repo and https://github.com/NewFrontDoor/crossroadshobart.org and is largely set up as required, just no data is being passed from the Sanity instance to the crossroadshobart.org/api route.

Someone familiar with NextJS API routes and AWS would best take this on.

[readeral]

Note this also impacts https://github.com/NewFrontDoor/new.onewaymargate.org