Restore versions DB table and add learning tests

db/migrate/20190302091059_restore_versions.rb

@@ -0,0 +1,15 @@
+class RestoreVersions < ActiveRecord::Migration
+  def change
+    drop_table :versions
+
+    create_table :versions do |t|
+      t.string :item_type, :null => false
+      t.integer :item_id, :null => false
+      t.string :event, :null => false
+      t.string :whodunnit
+      t.text :object
+      t.datetime :created_at
+    end
+    add_index :versions, [:item_type, :item_id]
+  end
+end

db/migrate/20190302111152_add_object_changes_to_versions.rb

@@ -0,0 +1,5 @@
+class AddObjectChangesToVersions < ActiveRecord::Migration
+  def change
+    add_column :versions, :object_changes, :jsonb
+  end
+end