Alkimi: Added support for Imp extention object

src/main/java/org/prebid/server/bidder/alkimi/AlkimiBidder.java

@@ -67,13 +67,16 @@ private ExtImpAlkimi parseImpExt(Imp imp) {
     private Imp updateImp(Imp imp, ExtImpAlkimi extImpAlkimi) {
         final Price bidFloorPrice = Price.of(imp.getBidfloorcur(), imp.getBidfloor());
 
+        final ObjectNode newExt = imp.getExt().deepCopy();
+        newExt.replace("bidder", makeImpExt(imp, extImpAlkimi));
+
         return imp.toBuilder()
                 .bidfloor(BidderUtil.isValidPrice(bidFloorPrice)
                         ? bidFloorPrice.getValue()
                         : extImpAlkimi.getBidFloor())
                 .instl(extImpAlkimi.getInstl())
                 .exp(extImpAlkimi.getExp())
-                .ext(makeImpExt(imp, extImpAlkimi))
+                .ext(newExt)
                 .build();
     }
 
@@ -82,7 +85,7 @@ private ObjectNode makeImpExt(Imp imp, ExtImpAlkimi extImpAlkimi) {
 
         extBuilder.adUnitCode(imp.getId());
 
-        return mapper.mapper().valueToTree(ExtPrebid.of(null, extBuilder.build()));
+        return mapper.mapper().valueToTree(extBuilder.build());
     }
 
     @Override

src/test/resources/org/prebid/server/it/openrtb2/alkimi/test-alkimi-bid-request.json

@@ -13,6 +13,7 @@
       },
       "bidfloor": 0.5,
       "ext": {
+        "tid": "${json-unit.any-string}",
         "bidder": {
           "token": "XXX",
           "bidFloor": 0.5,