Disallow a single dot in IDN hostnames

[OptimumCode]

Based on json-schema-org/JSON-Schema-Test-Suite#759 it is not allowed to have a single dot in the hostname (and IDN hostname). The hostname validator already had the correct behavior but the IDN hostname validator did not

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.55%. Comparing base (48fa0b4) to head (71c1591).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #247      +/-   ##
==========================================
+ Coverage   90.53%   90.55%   +0.02%     
==========================================
  Files         133      133              
  Lines        3983     3983              
  Branches     1059     1059              
==========================================
+ Hits         3606     3607       +1     
  Misses         82       82              
+ Partials      295      294       -1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.