[V3] How to get body for custom rest api endpoint

[EmilyYond]

It might just be a lack of documentation, but how do I set up a custom endpoint as per https://payloadcms.com/docs/rest-api/overview#custom-endpoints in version 3? Currently I have

import { NextResponse } from 'next/server'
...
endpoints: [
    {
      path: '/:id/generate',
      method: 'post',
      handler: async (req: PayloadRequest) => {
        try {
          console.log('req', req)

          return NextResponse.json(body, { status: 400 })
        } catch (error) {
          console.error(error)
        }
      },
    },
  ],

Which works but how do I get the body from the request? Sorry I am not that familiar with next/react so it might be obvious if you know!