Support impression-level GPID parameter

[bretg]

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

Publishers want to be able to specify the Global Placement ID (GPID) on the ad call. This is not currently possible through the SDK.

Describe the solution you'd like

Publishers should be able to specify the GPID for each impressions, and it gets passed to Prebid Server as imp[].ext.gpid

Originally, I was hoping that we could make this a generic ORTB parameter interface, but conversations around issue #877 revealed that the size of that request was slowing this smaller enhancement.

[bretg]

Thanks for the enhancement, but this needs a docs update... how do app developers make use of this?

[YuriyVelichkoPI]

Hi @bretg, @jsligh!

I'll update the docs soon. Not later than tomorrow.

[YuriyVelichkoPI]

Doc PR: prebid/prebid.github.io#4927

[bretg]

Sorry - I prematurely merged the original docs. Reverted. New PR prebid/prebid.github.io#4929 . Since the docs are waiting for release, will close the issue.