Add a patch to ActiveRecord::Migration

This patch does two things.

1. It adds migration versions to MiqRegion#ran_migrations as they
   are completed
2. It halts the global region migration process if the changes from
   the same migration in all the remote regions have not been replicated

This combination will allow us to ensure that the global region will
never attempt to replicate data which would be inconsistent with the
current schema.

Fixes https://bugzilla.redhat.com/show_bug.cgi?id=1601015

lib/extensions/ar_pglogical_migration.rb

@@ -0,0 +1,27 @@
+module ArPglogicalMigration
+  def migrate(direction)
+    PglogicalSubscription.all.each do |s|
+      provider_region = MiqRegion.find(s.provider_region)
+
+      while !provider_region.migrations_ran.include?(version) do
+        s.disable
+        s.enable
+        sleep 1
+        provider_region.reload
+      end
+    end
+
+    super(direction)
+
+    r = MiqRegion.my_region
+    if r.respond_to?(:migrations_ran=)
+      new_migrations = ActiveRecord::SchemaMigration.normalized_versions
+      new_migrations << version if direction == :up
+
+      r.migrations_ran = new_migrations
+      r.save
+    end
+  end
+end
+
+ActiveRecord::Migration.prepend(ArPglogicalMigration)