Static topics are the seeded topics that are automatically created for every Discourse instance to hold the content for the FAQ, ToS and Privacy pages. These topics are allowed to bypass the minimum title length checks when they're edited by admins:
ba27ee1637/app/assets/javascripts/discourse/app/models/composer.js (L487-L496)
However, on the server-side, the "quality title" validations aren't skipped for static topics and that can cause confusion for admins when they change the title of a static topic to something that's short enough to fail the quality title validations. This commit ignores all quality title validations on static topics when they're edited by admins.
Internal topic: t/75745.
It used to simply say "title is invalid" without giving any hint what
the problem could be. This commit adds different errors messages for
all caps titles, low entropy titles or titles with very long words.
This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.
Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging
introduce a couple of custom validators
fix minor discrepancies in tests
copy I18n error message keys to default location
clean up validation invocation
move some responsibilities out of validator into class
