Some optimization described in https://issues.redhat.com/browse/THREESCALE-10043 was already performed in https://github.com/3scale/porta/pull/3595

But the improvement is not sufficient, so this issue is for addressing the following:

Implement resync with batches.  We could add a new endpoint to applications.rb that receives a list of application ids and processes all of them in one request. This would require modifications in apisonator. We should modify the worker in porta to use that endpoint as well.