text/plain content-type on custom ARI response

[omkelderman]

If you set a custom ARI response as per #501, the http response you get has a content-type of text/plain instead of application/json. Correct me if I'm wrong but I'm pretty sure that is not according to expectations from https://datatracker.ietf.org/doc/draft-ietf-acme-ari/.

For completeness, these are the HTTP response headers from a request where the custom ARI response was not set:

cache-control: public, max-age=0, no-cache
content-type: application/json; charset=utf-8
link: <https://localhost:14000/dir>;rel="index"
retry-after: 21600
content-length: 107
date: Fri, 06 Jun 2025 11:41:43 GMT

And these are the HTTP response headers from a request where it was set:

cache-control: public, max-age=0, no-cache
link: <https://localhost:14000/dir>;rel="index"
content-type: text/plain; charset=utf-8
content-length: 110
date: Fri, 06 Jun 2025 11:42:44 GMT

I noticed the retry-after is also missing but I don't know if that is a problem or not.

[jsha]

Thanks for the report! I'll work on this.