Compute Migration Number Using Rails' Internals

[swiknaba]

https://github.com/dbl-works/checker/blob/main/lib/generators/dbl_checker/install_generator.rb#L11

replace hack

migration_version = `bundle exec rails g migration CreateDblChecks`[/db\/migrate\/(\d+)_/, 1]

with

ActiveRecord::Migration.next_migration_number(Kernel.rand(0..99))

see: https://apidock.com/rails/v6.1.3.1/ActiveRecord/Migration/next_migration_number