Record the default core bid ranking

[bretg]

As described in the response to the Audio/CTV committee requests, there's a proposal to define seatbid.bid.ext.prebid.rank as a way to flag the highest priority bids. A rank of "1" would mean highest priority. Note that highest priority doesn't always mean "highest price". Sometimes deals are prioritized over open market.

The 'response' document imagines a "bid ranking module" which would assign these ranks based on account configuration to cover advanced scenarios like "open market bids more than $5 above the deal price can beat out the deal, except for deal 123"

But at this point, neither Audio nor CTV needs support for that type of advanced scenario.

Since PBS-core is already sorting bids to apply ad server targeting, I'd like to explore adding the default seatbid.bid.ext.prebid.rank to every bid. Then someday, a more sophisticated bid ranking module could be built to override this default value.

The algorithm would be very basic:

• If ext.prebid.targeting.preferdeals is true, then sort by isDeal (true first) and then bid.price (highest first), else just bid.price (highest first).
• If bid.price is tied the sort order can be indeterminate
• loop through sorted bids
  • assign the current index to seatbid.bid.ext.prebid.rank. i.e. first bid gets 1, second 2, etc.