Multi-AdUnit Auctions

[bretg]

Is your feature request related to a problem? Please describe.

A performance optimization to consider for SDK 3.0 or a future release

Describe the solution you'd like

Currently Prebid SDK only ever invokes one imp at a time. This is inefficient from the perspective of both the app and the Prebid Server host company:

• the app has to deal with more requests/responses
• PBS has to process more requests than strictly necessary

Users of the SDK should be able to define an auction that includes multiple adunits. This applies to all the modes:

1. a global fetchDemand() that takes a list of AdUnit objects
2. for the rendering API, a global loadAd() that takes a list of AdUnit objects

Describe alternatives you've considered

Any reasonable multi-adunit solution is welcome.

[bretg]

Closing as duplicate of #950