SOA record email address with a dot in the mailbox name is not handled right

If you create a zone with an email address with a dot in the mailbox name, e.g.

openstack zone create example.com. --email "<email address hidden>"

then the dot in o.seibert is not handled correctly:

$ dig @ns03.cloud.syseleven.net. example.com SOA

; <<>> DiG 9.10.3-P4-Ubuntu <<>> @ns03.cloud.syseleven.net. example.com SOA
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 58004
;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1680
;; QUESTION SECTION:
;example.com. IN SOA

;; ANSWER SECTION:
example.com. 21600 IN SOA ns02.cloud.syseleven.net. o.seibert.xxsyselevenxx.de. 1562243380 21600 3600 259200 300

;; Query time: 7 msec
;; SERVER: 195.192.133.58#53(195.192.133.58)
;; WHEN: Thu Jul 04 12:29:48 UTC 2019
;; MSG SIZE rcvd: 126

The mailbox name should have its dot escaped, e.g. o\.seibert.xxsyselevenxx.de.
As it is, the SOA records represents the different email address <email address hidden>.

It can't be expected that the user specifies the email address in some pre-mangled form (and trying openstack zone create --email 'o\.<email address hidden>.' isn't even accepted).

I see this in the Ocata release, but looking at the source, this problem seems to exist also in today's HEAD:

./designate/schema/format.py:

@draft3_format_checker.checks("email")
@draft4_format_checker.checks("email")
def is_email(instance):
    if not isinstance(instance, compat.str_types):
        return True

    # A valid email address. We use the RFC1035 version of "valid".
    if instance.count('@') != 1:
        return False

    rname = instance.replace('@', '.', 1)

    if not re.match(RE_ZONENAME, "%s." % rname):
        return False

    return True

designate/central/service.py:

    # SOA Recordset Methods
    def _build_soa_record(self, zone, ns_records):
        return "%s %s. %d %d %d %d %d" % (ns_records[0]['hostname'],
                                          zone['email'].replace("@", "."),
                                          zone['serial'],
                                          zone['refresh'],
                                          zone['retry'],
                                          zone['expire'],
                                          zone['minimum'])

Both fragments replace the first @ by a . but don't do any other fixups.