FQDN_REGEX cannot match host names that have single-letter subdomains

[lunkwill42]

The problem

We have all of our CNaaS equipment on the .c.uninett.no domain. This is not supported by CNaaS-NMS, rendering us unable to use any setting that is validated by Pydantic using host_schema fields.

The source here is this:

cnaas-nms/src/cnaas_nms/db/settings_fields.py

Line 22 in f9f2f94

FQDN_REGEX = r"([a-zA-Z0-9-]{1,63}\.)([a-z-][a-z0-9-]{1,62}\.?)+"

To reproduce

>>> import re
>>> from cnaas_nms.db import settings_fields as sf
>>> pattern = re.compile(sf.FQDN_REGEX)
>>> pattern.match("test.c.uninett.no")
>>> pattern.match("test.cd.uninett.no")
<re.Match object; span=(0, 18), match='test.cd.uninett.no'>