Added Data Cleanrooms Guidelines for Public Comment

[wittjill]

#2 Adds a new extension document to the ECAPI standard. It focuses on Data Cleanroom Use Cases and data formatting standards for transport. Please leave comments/corrections here.

[newbiechris741]

The whole conversion concept is fundamentally flawed. It doesn't take into account basic marketing principles that have tested time and time again from Les Binet, Peter Fields and Ehrenberg Bass. Brand strength and size determine most conversions. Price matters and promotions. All CAPI does is link an ID between some (but not all!) media exposure and sales (many of which were generated elsewhere). Duplication matters but multi-touch also shares the same problems. Data clean rooms are unnecessary. They are just more spend gobbling tech that can be avoided through probabilistic means anyhow. Plus by the time the DCR is done co-horting, adding noise and other privacy preserving means it might as well be probablistic. and Multiple email/single user + single email/multiple user.