LPS-44593 Decoupling SubscriptionSender from services. 

Hey @rotty3000  (cc/ @sergiogonzalez)

I've been working in some bugs related with subscriptions and I've found some weird logic that coupled services and SubscriptionSender.

The old logic forced developers to know that when they were setting the list of subscriptions (calling addPersistedSubscribers method), if they would like to check for the entity permissions, they had to add as last object of that list an OVP with the className and the classPK (or in some cases resourceIds or groupIds) of this entity.

I think that services shouldn't have to do this kind of operations (I mean logic should be decoupled enough to no t fail depending on the order of the objects of a list) and the SubscriptionSender API should be clearer and "smarter", so I decided to pass this last object in a different method and create a separate field for this.

What do you think?

Thanks!!