CleanUp: Add `#destroy_empty`6854-clean-up--destroy-routes-outside-referential

Gives us a single call site to trigger the destruction of vehicle
journeys, journey patterns, and routes without content.

This was previously done directly in the `#clean` method, but since it's
not needed during referential duplication (only during merges), we don't
want to enable it by default. Thus now to activate the same old
functionality, you would create a `CleanUp` like this:

    CleanUp.new(methods: [:destroy_empty])

Refs #6854

1 files changed, 12 insertions, 0 deletions

diff --git a/spec/models/clean_up_spec.rb b/spec/models/clean_up_spec.rb
index f0c3a3233..f39ca2f2b 100644
--- a/spec/models/clean_up_spec.rb
+++ b/spec/models/clean_up_spec.rb
@@ -297,6 +297,18 @@ RSpec.describe CleanUp, :type => :model do
     end
   end
 
+  describe "#destroy_empty" do
+    it "calls the appropriate destroy methods" do
+      cleaner = create(:clean_up)
+
+      expect(cleaner).to receive(:destroy_vehicle_journeys)
+      expect(cleaner).to receive(:destroy_journey_patterns)
+      expect(cleaner).to receive(:destroy_routes)
+
+      cleaner.destroy_empty
+    end
+  end
+
   describe "#run_methods" do
     let(:cleaner) { create(:clean_up) }