Signature Language Updates

As discussed previously on the list several times, the editors of the signatures draft have gone through and tried to clean up the language within the signatures draft. Namely, we’ve stopped using the problematic term “covered content” in favor of “covered components”, or more fully, “HTTP Message Signature Covered Components” or “Message Components” or other variations as needed by surrounding text.

This is implemented in the following PR:

https://github.com/httpwg/http-extensions/pull/1599 <https://github.com/httpwg/http-extensions/pull/1599>

This PR also cleans up sloppy language that used “header” where we really meant “field”, and a few other small things. No syntax changes have been made to the draft here, and no changes to the coded examples.

 — Justin