Adding granular controls for app categories and specific ads at impression level (equivalent to BidRequest.acat/bcat)

[benhumphry]

permitted/blocked advertiser categories and specified apps

The following proposed changes are already widely adopted and in use by mobile advertising platforms:

The advertisers, ad platforms and SSPs focused on mobile ads, such as Ocean Engine, Kuaishou Technology, Meitu, are using these parameters in almost all of their bid requests, and bid responses.
These provide more fine-grain control over which ads can appear in specific apps and ad positions, allowing better user experience, brand protection and to better meet regulatory requirements.
These proposed changes will align OpenRTB 2.6.x with this real world usage.