When registering an account I stumbled upon urn:ietf:params:acme:error:agreementRequired. This error code does not seem to appear in https://www.iana.org/assignments/acme/acme.xhtml#acme-error-types. Section 6.7 "Errors" of RFC8555 says:

Servers MUST NOT use the ACME URN namespace for errors not listed in the appropriate IANA registry [...].

Is there some standard that I am missing which defines this error code (which did not propagate into the IANA registry yet)?