Support banner

This page will accommodate the new adapter design, to support banner (display) type media, in our adapter

Things to consider

Phase 1

General structure change

• []Add banner type to supported media type
• Update endpoint to the new hb-multi
• Create the new imp object to send
• Change GET request to POST (and verify old behavior is not affected and destroyed)
• Find what's common between video and banner request and reuse data when building object

function specific

• isBidRequestValid - does is need to be changed for multiple bids? is there a different validation for banners?
• build request - what's needed for a banner request compared to video?

Phase 2

• Create a test object and test endpoint