Added realtime event methods for related products/content models.

[ashirgaokar]

Q	A
Bug fix?	no
New feature?	no
BC breaks?	no
Related Issue	no
Need Doc update	yes

Describe your change

For sending real-time event methods for related products/content models, I added the following missing methods:

• add_to_cart_object_ids
• add_to_cart_object_ids_after_search
• purchased_object_ids
• purchased_object_ids_after_search

What problem is this fixing?

Unable to send real-time events for the following (event-type , sub-event-type) combinations associated with the related products/content models:

• conversion, addToCart
• conversion, purchase