Switch DatabaseCleaner strategy to :deletion.
Switch DatabaseCleaner strategy to :deletion.

This greatly improves the speed of the test suite.

`DatabaseCleaner.strategy = :transaction`:

    docker-compose exec web bin/rspec  0,56s user 0,21s system 0% cpu 24:25,34 total

`DatabaseCleaner.strategy = :deletion`:

    docker-compose exec web bin/rspec  0,38s user 0,14s system 0% cpu 4:01,60 total

bjoernalbers/faxomat,bjoernalbers/faxomat,bjoernalbers/faxomat,bjoernalbers/faxomat