iOS Mobile SDK: Support advertiserId in response

[karnowski]

Background

Recently the Kevel ad servers started including the advertiserId for each winning ad. We should expose that ID via the iOS SDK PlacementDecision object too.

Here's an example snippet, note the new advertiserId value:

{
  "user": { "key": "abc" },
  "decisions": {
    "div0": [
      {
        "adId": 2104402,
        "creativeId": 1773302,
        "flightId": 2583477,
        "campaignId": 502103,
        "advertiserId": 163756,
        "priorityId": 99645,
        "clickUrl": "https://e-23.adzerk.net/r?e=ey....",
        "impressionUrl": "https://e-23.adzerk.net/i.gif?e=ey....",
        "contents": [
          {
          }
        ],
        "height": 250,
        "width": 300,
        "events": []
      }
    ]
  }
}

Acceptance Criteria

• As an integrating developer using the Kevel iOS SDK, I can access the advertiser ID for each decision returned.