CAA accounturi and validationmethods parameters

[srdavidson]

There is a proposal (see cabforum/servercert#567) to amend the CAA requirements in the TLS BR roughly as follows:

Effective DATE, when processing CAA records, CAs MUST process the accounturi and validationmethods parameters as specified in RFC 8657. In addition:

• If the CA accepts certificate requests via any protocol other than the ACME protocol defined in RFC 8555, the CA MUST define the recognized format of the accounturi in this Section 3.2.2.8 of their CPS.
• The CA MUST define each recognized validationmethods label, along with the corresponding Section 3.2.2.4 subsection number, in this Section 3.2.2.8 of their CPS. Labels MUST comply with Section 4 of RFC 8657.

Depending on the outcome of that proposal, the SMCWG may consider adding a corresponding requirement to the S/MIME BR section 3.2.2.8.

[srdavidson]

Note that the Server Cert proposal has been amended to include new requirements for DNSSEC as well: https://github.com/cabforum/servercert/pull/567/files