This PR fixes #10409 (the first, trivial, commit) and refactors the code used to join a region so that it is testable and easier to understand.

Before this change, join_region.rb would always fail, but it was also called in a strange way in order to get the code to execute in the rails environment (Using AwesomeSpawn calling bin/rails runner join_region.rb).

Because it was a plain ruby script it was also not tested (nor easily testable).

This PR makes the join region logic a rake task which has its body implemented in evm_application.rb which can easily be tested.
This also simplifies the logic greatly as we can use ApplicationRecord directly to retrieve the region number from the database configured in database.yml at the time the rake task is called.