With this fix, we will try latest changes in Rails 5.2 together with standard auto-generated secret_key_base in development as a fallback.
If no specified key found, auto-generated value will be used instead.
When supporting Rails 5.2 credentials on
https://github.com/plataformatec/devise/pull/4712, we ended up breaking
apps that were upgraded to Rails 5.2 and weren't using `credentials`
to store their `secret_key_base`. See
https://github.com/plataformatec/devise/issues/4807 for more context.
To fix it, we're now checking whether the key is present before using it.
Since there weren't any automated test for this - the conditionals were
in a Rails engine initializer - I've extracted it to a new class so that
we are able to test it easily.
Fixes#4807
Gencer W. Genç