Add support to pass custom key in Prebid cache request

src/videoCache.js

@@ -60,11 +60,17 @@ function wrapURI(uri, impUrl) {
  */
 function toStorageRequest(bid) {
   const vastValue = bid.vastXml ? bid.vastXml : wrapURI(bid.vastUrl, bid.vastImpUrl);
-  return {
+  let payload = {
     type: 'xml',
     value: vastValue,
     ttlseconds: Number(bid.ttl)
   };
+
+  if (typeof bid.customCacheKey === 'string' && bid.customCacheKey !== '') {
+    payload.key = bid.customCacheKey;
+  }
+
+  return payload;
 }
 
 /**
@@ -114,7 +120,7 @@ function shimStorageCallback(done) {
  *
  * @param {CacheableBid[]} bids A list of bid objects which should be cached.
  * @param {videoCacheStoreCallback} [done] An optional callback which should be executed after
- *   the data has been stored in the cache.
+ * the data has been stored in the cache.
  */
 export function store(bids, done) {
   const requestData = {

test/spec/videoCache_spec.js

@@ -122,6 +122,43 @@ describe('The video cache', function () {
       assertRequestMade({ vastXml: vastXml, ttl: 25 }, vastXml);
     });
 
+    it('should make the expected request when store() is called while supplying a custom key param', function () {
+      const customKey1 = 'keyword_abc_123';
+      const customKey2 = 'other_xyz_789';
+      const vastXml1 = '<VAST version="3.0">test1</VAST>';
+      const vastXml2 = '<VAST version="3.0">test2</VAST>';
+
+      const bids = [{
+        vastXml: vastXml1,
+        ttl: 25,
+        customCacheKey: customKey1
+      }, {
+        vastXml: vastXml2,
+        ttl: 25,
+        customCacheKey: customKey2
+      }];
+
+      store(bids, function () { });
+      const request = requests[0];
+      request.method.should.equal('POST');
+      request.url.should.equal('https://prebid.adnxs.com/pbc/v1/cache');
+      request.requestHeaders['Content-Type'].should.equal('text/plain;charset=utf-8');
+      let payload = {
+        puts: [{
+          type: 'xml',
+          value: vastXml1,
+          ttlseconds: 25,
+          key: customKey1
+        }, {
+          type: 'xml',
+          value: vastXml2,
+          ttlseconds: 25,
+          key: customKey2
+        }]
+      };
+      JSON.parse(request.requestBody).should.deep.equal(payload);
+    });
+
     function assertRequestMade(bid, expectedValue) {
       store([bid], function() { });