Type of change

• Feature

Description of change

This adds support for the ORTB protected audience extensions:

• when PAAPI is enabled, bid requests' ortb2Imp.ext.igs is populated (similar and in addition to ext.ae)
• bid adapters can reply with buyers (igb) objects in additon to auction configs (config). The fledgeAuctionConfigs response property is migrated to paapi. for example:

    // current response from interpetResponse, returning an auction config
   return {bids: [...], fledgeAuctionConfigs: [{bidId: 'xxx', config: {...}}]}
  
   // equivalent to the above, using `paapi`
   return {bids: [...], paapi: [{bidId: 'xxx', config: {...}}]}
  
   // return a buyer (igb) object instead of a full auction config
   return {bids: [...], paapi: [{bidId: 'xxx', igb: {...}}]}
  

• ortbConverter can now parse responses' ext.igi to generate a paapi array.
• publishers can set up auctions to run igb with:

   pbjs.setConfig({
      paapi: {
         enabled: true,
         componentSeller: {
            auctionConfig: {
                  decisionLogicURL: 'publisher.example'
                  // ...
            }
         }
      }
   })
  

• if paapi.componentSeller.auctionConfig is set, we attempt to collect all IGB objects into a single auction config, which is then treated like any other auction config for the purpose of getPAAPIConfig/setPAAPIConfigForGPT.
• it's possible for IGB objects to be incompatible with each other (same origin, different signals). In this case we split the conflicts into a second (or third, etc) auction config.
• Because IGB objects come from different adapters, and first-party data (ortb2/ortb2Imp) can vary by adapter, auction configs generated from IGB have it set in perBuyerSignals instead of auctionSignals. "Normal" auction configs also have first party data repeated in perBuyerSignals, for consistency.
• Instead of one auction config (minus conflicts), it's possible to generate one for each bidder with

   pbjs.setConfig({
       paapi: {
           enabled: true,
           componentBuyers: {
                separateAuctions: true,
                auctionConfig: {/* ... */}
           }
       }
   })
  

  In this case, auctionSignals is populated with first party data as usual.

Other information

Closes #11131
Closes #11094