Shortening the query string params, adding BIDID macro

[bretg]

The goal is to save on the number of bytes we're sending to the ad server. The differences between this and the original version are:

• shortening query string params to one char
• removed the bidder param
• added BIDID as a macro to hb_winurl

Original version is at https://github.com/prebid/prebid-server/files/2946568/Prebid.Server.Event.Notifications.-.Tech.Spec.pdf

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[guscarreon]

• In the "New endpoint" section in the first page it says the GET endpoint will allow web browsers to notify about different ad events. Shouldn't it say to "be notified"? In a GET endpoint they'll pull the information, not push it.
• Shouldn't this document describe the difference between the win and view events?
• If this is a GET endpoint, why does the 200 endpoint is understood as the event notification being accepted and delivered for processing? Doesn't that sort of action correspond to a POST endpoint?
• "Description" section first paragraph seems to have an extra newline.

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This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[bretg]

As for GET-vs-POST. I get your point, but:

• POSTs cause the browser to do two fetches: OPTIONS and then POST
• The most common mechanism of dropping a tracking pixel is an 'img src' which is a GET. That's how this endpoint is hit -- img src="pbs.my.com/event/t=win&f=i

So we shouldn't change to POST. Did made some modifications and moved it to github wiki -- https://github.com/prebid/prebid-server/wiki/Prebid-Server-Event-Notification-Tech-Spec

• changed 'view' event to 'imp' and explained
• added new column in accounts table in the DB