Rubicon: Remove default maxbids value (prebid#4041)

Author: AntoxaAntoxic

src/main/java/org/prebid/server/bidder/rubicon/RubiconBidder.java

@@ -890,15 +890,14 @@ private List<String> mapVendorsNamesToUrls(List<Metric> metrics) {
         return vendorsUrls.isEmpty() ? null : vendorsUrls;
     }
 
-    private Integer getMaxBids(ExtRequest extRequest) {
+    private static Integer getMaxBids(ExtRequest extRequest) {
         final ExtRequestPrebid extRequestPrebid = extRequest != null ? extRequest.getPrebid() : null;
         final List<ExtRequestPrebidMultiBid> multibids = extRequestPrebid != null
                 ? extRequestPrebid.getMultibid() : null;
         final ExtRequestPrebidMultiBid extRequestPrebidMultiBid =
                 CollectionUtils.isNotEmpty(multibids) ? multibids.getFirst() : null;
-        final Integer multibidMaxBids = extRequestPrebidMultiBid != null ? extRequestPrebidMultiBid.getMaxBids() : null;
 
-        return multibidMaxBids != null ? multibidMaxBids : 1;
+        return extRequestPrebidMultiBid != null ? extRequestPrebidMultiBid.getMaxBids() : null;
     }
 
     private String getGpid(ObjectNode impExt) {

src/test/java/org/prebid/server/bidder/rubicon/RubiconBidderTest.java

@@ -599,7 +599,7 @@ public void makeHttpRequestsShouldPassNativeBattrField() {
     }
 
     @Test
-    public void makeHttpRequestsShouldAddMaxbidsAttributeAsOneIfExtPrebidMultibidMaxBidsIsNotPresent() {
+    public void makeHttpRequestsShouldAddMaxbidsAttributeAsNullIfExtPrebidMultibidMaxBidsIsNotPresent() {
         // given
         final BidRequest bidRequest = givenBidRequest(
                 builder -> builder.ext(ExtRequest.of(ExtRequestPrebid.builder()
@@ -620,7 +620,7 @@ public void makeHttpRequestsShouldAddMaxbidsAttributeAsOneIfExtPrebidMultibidMax
                 .extracting(Imp::getExt).doesNotContainNull()
                 .extracting(ext -> mapper.treeToValue(ext, RubiconImpExt.class))
                 .extracting(RubiconImpExt::getMaxbids)
-                .containsExactly(1);
+                .containsOnlyNulls();
     }
 
     @Test
@@ -659,7 +659,6 @@ public void makeHttpRequestsShouldFillImpExt() {
                                 null,
                                 "uuid_bid_id"))
                         .skadn(givenSkadn)
-                        .maxbids(1)
                         .build());
     }
 
@@ -2445,7 +2444,6 @@ public void makeHttpRequestsShouldCreateRequestPerImp() {
                         .video(Video.builder().build())
                         .ext(mapper.valueToTree(RubiconImpExt.builder()
                                 .rp(expectedImpExtRp)
-                                .maxbids(1)
                                 .build()))
                         .build()))
                 .build();
@@ -2456,7 +2454,6 @@ public void makeHttpRequestsShouldCreateRequestPerImp() {
                         .ext(mapper.valueToTree(
                                 RubiconImpExt.builder()
                                         .rp(expectedImpExtRp)
-                                        .maxbids(1)
                                         .build()))
                         .build()))
                 .build();

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

@@ -28,7 +28,6 @@
             "mint_version": ""
           }
         },
-        "maxbids": 1,
         "tid": "${json-unit.any-string}"
       }
     }

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

@@ -28,7 +28,6 @@
             "mint_version": ""
           }
         },
-        "maxbids": 1,
         "tid": "${json-unit.any-string}"
       }
     }