DB schema generated by a migration may look different in
rails 4 and 5 (because rails 5 may use different default values).
For this reason it's important to explicitly set for which rails
version a migration was written for.
See https://stackoverflow.com/questions/35929869/activerecordmigration-deprecation-warning-asks-for-rails-version-but-im-no/35930912#35930912
Given the user can soon have multiple config sources for CI, we now store
what type at the time of the pipeline run we chose. This will give us
insight into what triggered the new pipeline so we can display it to the
enduser.
