Identify intended recipient for RateLimit fields

[ioggstream]

Discussion

Oblivious Proxy Feedback https://github.com/tireddy2/ohai/blob/main/draft-rdb-ohai-feedback-to-proxy-02.txt relies on this spec to convey service limit information between oblivious resources and oblivious proxy.

The ohai-target parameter identify that the RateLimit fields are intended for the Oblivious proxy: in this case such proxy MUST strip the RateLimit before forwarding the response to the client.

This interesting usage poses some questions, for example:

1. does the current specification require some tweaks to support similar use cases? Since we just care about syntax and semantics of those fields, it could not be the case but further investigations should be made;
2. is a general mechanism to identify the intended recipient of the RateLimit fields useful? Is it necessary for the current specification status? Can it be deferred to further specifications?

While no normative changes can be required, it is possible that some editorial adjustments can be useful though. cc: @tireddy2 @unleashed