Foreman » Installer

Rewrite migration spec

This refactors the migration spec to be more focused on the actual
testing by removing a lot of duplication.

In places where there is very little in the actual fixture, the test is
rewritten to test it inline or provide the answers inline. This makes it
easier to follow what's going on.

Care has been taken to get decent naming in the output:

$ bundle exec rspec --format documentation spec/migration_spec.rb

with all migrations
      on the scenario
        foreman
          does not change the scenario config
          does not change the scenario answers
        foreman-proxy-content
          does not change the scenario config
          does not change the scenario answers
        katello
          does not change the scenario config
          does not change the scenario answers
      on katello
        with fixture pulpcore-migration
          matches the answers fixture
        with fixture pulpcore-migration-rpm-only
          matches the answers fixture
        with fixture pulpcore-migration-dont-use-content-plugins-on-upgrades
          matches the answers fixture
      the migration 20210625142707_dynamic_puppet_in_foreman_groups
        on foreman
          removes puppet
        on katello
          removes puppet
      the migration 200818160950-remove_tuning_fact on foreman-proxy-content
        removes facts
      the migration 20210929144850_disable_puppet_plugins_if_undesired
        on foreman
          keeps foreman::cli disabled
          adds foreman::cli::puppet disabled
          keeps foreman disabled
          adds foreman::plugin::puppet disabled
        on katello
          keeps foreman::cli disabled
          adds foreman::cli::puppet disabled
          keeps foreman disabled
          adds foreman::plugin::puppet disabled
      the migration 181213211252-merged-installer
        on foreman-proxy-content
          matches the scenario fixture
        on katello
          matches the scenario fixture

Finished in 0.6798 seconds (files took 0.27722 seconds to load)
    22 examples, 0 failures

This makes it possible to find out where it failed. Errors look like
this:

Failures:

1) with all migrations the migration 20210625142707_dynamic_puppet_in_foreman_groups on foreman removes puppet
         Failure/Error: expect(migrated_answers['foreman']['user_groups']).to eq ['a']

expected: ["a"]
got: []

1. ./spec/migration_spec.rb:57:in `block (5 levels) in <top (required)>'
2. /usr/share/gems/gems/bundler-2.2.22/libexec/bundle:49:in `block in <top (required)>'
3. /usr/share/gems/gems/bundler-2.2.22/libexec/bundle:37:in `<top (required)>'

(compared using ==)

Technically the migration has a different name on Foreman and Katello,
but that's somewhat easy to figure out and painful to solve so it has to
be taken for granted now.