Modal errors as objects are introduced:
https://github.com/rails/rails/pull/32313

model.errors.first returns ActiveModel::Error object
that's why model.errors.first[1] doesn't work in Rails 6.1

We need a way that works both for 6.1 and 6.0 in order to
introduce changes gradually:

model.errors.values.first works for both versions.

Even though treating errors as a hash is deprecated it works
so we can introduce the changes in 6.0 and then fix the
deprecations when we're on 6.1

(cherry picked from commit b5ecc309314429040921233d4a6216655fede089)