Add RAINBOW_TRUSTLESS_GATEWAY_DOMAINS=trustless-gateway.link

[lidel]

Problem

• https://trustless-gateway.link should be limited to trustless responses.
• Right now rainbow allows deserialized responses for all domains, so the limiting of response types to trustless car/block/ipns-record on that domain is done at Nginx, which is a bit janky.
  • For example, it does support Accept: application/vnd.ipld.car but errors on ?format=car, which is a bug we need to fix eventually.

Solution

I believe explicit is better than implicit here.

Initial idea: We already have RAINBOW_SUBDOMAIN_GATEWAY_DOMAINS. Add similar, explicit RAINBOW_TRUSTLESS_GATEWAY_DOMAINS which limits specified domains to only support trustless responses, and return HTTP 400 Bad Request for everything else, and use it with trustless-gateway.link

cc @ns4plabs @hacdias