Callout body via Lua code

callout.json

{
	"name": "request-callout",
	"config": {
		"callouts": [
			{
				"name": "c1",
				"request": {
					"url": "https://httpbin.org/anything",
					"method": "POST",
					"body": {
						"custom": {},
						"decode": false,
						"forward": true
					},
					"by_lua": "local body_json = '{\"id\": \"foobar\"}'; kong.ctx.shared.callouts.c1.request.params.body = body_json"
				},
				"response": {
					"body": {
						"decode": true
					},
					"by_lua": "kong.log.inspect(kong.ctx.shared.callouts.c1.response.body)"
				}
			}
		],
	   "upstream": {
		}
	}
}