POST /api-redirect fails with 500

POST /api-reponse-redirect-307 fails with 500

POST /api-reponse-redirect works

POST /non-existent-path fails with 500 (should be 404)

POST + redirect we should do a 303 as it seems:https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/303. Otherwise POST + body are used on the redirect (the / page here) and will generate a 500. We may want a better error message too, along with fixing redirect().