`sole` Method Is Going to Be Introduced into ActiveRecord and Enumerable
Today I learned that Rails 6.1.3 does not have methods that raise exceptions when more than one record was found. However, in future versions, we could use ActiveRecord::FinderMethods#sole for that purpose. It seems Enumerable#sole is also going to be introduced.
Sometimes I need to make sure there is one and only one record that matches a condition without using a unique-index, for example, when I cannot add that constraint to the database.
