Migrate the existing checker / suggester code to instead use the new validator framework. We need to add,

1. A validator for variables in format - %(parent_url)s, %(review_date)s that is enforced and insertable.
2. A validator for variables in format - {access_url}, {partner} that is enforced and insertable.
3. An insertable (not enforced) for HTML tags. The source translation has anchor, small tags.

We'll need to update the YAML configuration file located here - https://phabricator.wikimedia.org/diffusion/GTWN/browse/master/groups/

Documentation: https://www.mediawiki.org/wiki/Help:Extension:Translate/Validators
Example patch: https://gerrit.wikimedia.org/r/c/translatewiki/+/549930