Hookup ndjson to HTTP delegated routing

[masih]

streaming is implemented for all backend but missing hookup for HTTP delegated routing endpoints.

[guseggert]

Note that Kubo will ship support for ndjson soon, and it will default to Accept=application/x-ndjson,application/json, which means that when the cid.contact deployment happens then clients will all immediately flip over to ndjson. This isn't necessarily a problem, just something that should be tested w/ Kubo before deploying to cid.contact. If for some reason the intgration w/ kubo is broken then you risk breaking all kubo clients.