PremiumFeatureNotAllowed: Your current plan doesn’t allow for custom domains.

[sentry-io]

Sentry Issue: APPLICATION-BACKEND-748

PremiumFeatureNotAllowed: Your current plan doesn’t allow for custom domains.
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  File "emails/models/external_feed/actions/check_for_updates.py", line 58, in call
    handle_failure(feed)
  File "emails/models/external_feed/actions/check_for_updates.py", line 30, in handle_failure
    feed.save()
  File "emails/signals/external_feed.py", line 22, in external_feed_automation_creation_actions
    newsletter.save()
  File "emails/models/newsletter/model.py", line 953, in save
    self.full_clean()
  File "emails/models/newsletter/model.py", line 929, in full_clean
    raise PremiumFeatureNotAllowed(