rtd modules: adjust timing of settargeting methods

[patmmccann]

This is a great point, we should put this in our cove review guidelines and open an issue to fix the 2-3 you mention

Originally posted by @patmmccann in #14636 (comment)

We should fix relevad and sirdata as mentioned in this thread

[dgirardi]

After looking into this I'm not sure that #14711 is not breaking, it's possible that they were setting slot targeting directly for the same reason as #14636 (wanting targeting set regardless of what happens in the prebid auction). However if that's the case relevad and sirdata could use page level targeting, since they're setting the same targeting data on every slot.

#14636 is different as the targeting depends on the ad unit.

Currently:

1. both ad units and bid responses can specify adserverTargeting, a map from targeting keys to arbitrary values.
2. RTD modules can provide a getTargetingData method. If they do, it's called when the auction ends and the targeting is added to adUnit.adserverTargeting.
3. When prebid computes targeting, which happens after one of the getAdserverTargeting or setTargeting API methods is called, it looks at both ad units and bid responses' adserverTargeting.

The issue is that if a publisher is using a "failsafe" timeout that refreshes GPT slot before the Prebid auction completes, (3) does not happen in time and GAM does not see the targeting.

Proposal:

• when the auction starts (auctionInit), prebid updates slot targeting using adUnit.adserverTargeting and customSlotMatching.
• everything above is left unchanged; when the auction ends, adUnit.adserverTargeting is again included in "final" targeting.
• RTD modules that wish to set targeting at auction init can update reqBidsConfigObj.adUnits[].adserverTargeting in `getBidRequestData.
• Deprecate any new use of RTD's getTargetingData. It's arguably already redundant as RTD modules can update adUnit.adserverTargeting as per the point above, and despite it happening later it is not provided with any more information than getBidRequestData.

[patmmccann]

bid related targeting clearing should also happen at init

[patmmccann]

we're inclined to keep getTargetingData as an option so if anyone prefers setting on auctionDone, they can keep that behavior