Support for stored auction and bid response ids

[eros902002]

Github issue #228

This PR contains the following changes:

• Add methods on Prebid to set stored auction id and stored bid responses ids.
• If present, add these params into the ext object of the impression on the OpenRTB request to Prebid server.

Setting Stored Auction Id - Single Stored Auction Response ID

API:

var storedAuctionResponse: String

Example

Swift:

Prebid.shared.storedAuctionResponse = "111122223333"

Objective-C:

Prebid.shared.storedAuctionResponse = @"111122223333";

Will generate on the request:

"imp": [
    {
        "id": "a",
        "ext": {
            "prebid": { 
                "storedauctionresponse": { 
                    "id": "111122223333" 
                 } 
             } 
        }
    }
]

Setting Stored Bid Responses Ids - Multiple Stored Bid Response IDs

API:

func addStoredBidResponse(bidder: String, responseId: String)
func clearStoredBidResponses()

Example

Swift:

Prebid.shared.addStoredBidResponse(bidder: "appnexus", responseId: "221144")
Prebid.shared.addStoredBidResponse(bidder: "rubicon", responseId: "221155")

Objective-C:

[Prebid.shared addStoredBidResponseWithBidder:@"appnexus" responseId:@"221144"];
[Prebid.shared addStoredBidResponseWithBidder:@"rubicon" responseId:@"221155"];

Will generate on the request:

"imp": [
    {
      "id": "a",
      "ext": {
          "prebid": {
            "storedbidresponse": [
                  { "bidder": "appnexus", "id": "221144" },
                  { "bidder": "rubicon", "id": "221155" },
             ]
           } 
      }
    }
  ]

This method was created to clear the stored bid response ids:

Prebid.shared.clearStoredBidResponses()

[yoalex5]

Hello @eros902002 !

Thank you for the PR.
I have proposed my changes in PR

[yoalex5]

Looks good!
Thanks