Response headers should use consistent separators

[sbweeden]

The Sec-Session-Registration example response header is shown with several elements, separated by semi-colons:

Sec-Session-Registration: "path";challenge=:Y2hhbGxlbmdl:;es256;rs256;authorization=:YXV0aGNvZGU=:

The Sec-Session-Challenge example response header is shown with two elements, separated by a comma:

Sec-Session-Challenge: session_identifier=<session identifier>,challenge=<base64url encoded challenge>

Can we just use a consistent separator for both response headers?