fixup after 4th review

Author: mbonnafon

src/main/java/org/prebid/server/bidder/mobkoi/MobkoiBidder.java

@@ -32,7 +32,6 @@
 import java.util.List;
 import java.util.Objects;
 import java.util.Optional;
-import java.util.stream.Collectors;
 
 public class MobkoiBidder implements Bidder<BidRequest> {
 
@@ -50,7 +49,6 @@ public MobkoiBidder(String endpointUrl, JacksonMapper mapper) {
 
     @Override
     public Result<List<HttpRequest<BidRequest>>> makeHttpRequests(BidRequest bidRequest) {
-
         final Imp firstImp = bidRequest.getImp().getFirst();
 
         final ExtImpMobkoi extImpMobkoi;
@@ -87,15 +85,18 @@ private Imp modifyImp(Imp firstImp, ExtImpMobkoi extImpMobkoi) {
 
         if (StringUtils.isNotBlank(extImpMobkoi.getPlacementId())) {
             return firstImp.toBuilder().tagid(extImpMobkoi.getPlacementId()).build();
-        } else {
-            throw new PreBidException("invalid because it comes with neither request.imp[0].tagId nor "
-                    + "req.imp[0].ext.Bidder.placementId");
         }
+
+        throw new PreBidException("invalid because it comes with neither request.imp[0].tagId nor "
+                    + "req.imp[0].ext.Bidder.placementId");
     }
 
+    // url is already validated with `bidder-params` json schema
     private String resolveEndpoint(String customUri) {
         try {
-            HttpUtil.validateUrl(customUri);
+            if (customUri == null) {
+                return endpointUrl;
+            }
             final URI uri = new URI(customUri);
             return uri.resolve("/bid").toString();
         } catch (IllegalArgumentException | URISyntaxException e) {
@@ -148,6 +149,6 @@ private static List<BidderBid> bidsFromResponse(BidResponse bidResponse) {
                 .filter(Objects::nonNull)
                 .flatMap(Collection::stream)
                 .map(bid -> BidderBid.of(bid, BidType.banner, "mobkoi", bidResponse.getCur()))
-                .collect(Collectors.toList());
+                .toList();
     }
 }

src/test/java/org/prebid/server/bidder/mobkoi/MobkoiBidderTest.java

@@ -25,6 +25,7 @@
 
 import static java.util.Arrays.asList;
 import static java.util.Collections.singletonList;
+import static java.util.function.UnaryOperator.identity;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
 import static org.prebid.server.bidder.model.BidderError.badInput;
@@ -80,7 +81,7 @@ public void makeHttpRequestsShouldAddPlacementIdOnlyInFirstImpressionTagId() {
         // given
         final ObjectNode mobkoiExt = impExt("pid", null);
         final Imp givenImp1 = givenImp(impBuilder -> impBuilder.ext(mobkoiExt));
-        final Imp givenImp2 = givenImp(impBuilder -> impBuilder);
+        final Imp givenImp2 = givenImp(identity());
         final BidRequest bidRequest = BidRequest.builder().imp(asList(givenImp1, givenImp2)).build();
 
         // when
@@ -108,20 +109,6 @@ public void makeHttpRequestsShouldUseConstructorEndpointWhenNoCustomEndpointIsDe
         assertThat(results.getErrors()).isEmpty();
     }
 
-    @Test
-    public void makeHttpRequestsShouldConstructorEndpointWhenTheCustomIsInvalidInMobkoiExtension() {
-        // given
-        final ObjectNode mobkoiExt = impExt("pid", "invalid-URI");
-        final BidRequest bidRequest = givenBidRequest(impBuilder -> impBuilder.ext(mobkoiExt));
-
-        // when
-        final Result<List<HttpRequest<BidRequest>>> result = target.makeHttpRequests(bidRequest);
-
-        // then
-        assertThat(result.getValue()).extracting(HttpRequest::getUri).containsExactly("https://test.endpoint.com/bid");
-        assertThat(result.getErrors()).isEmpty();
-    }
-
     @Test
     public void makeHttpRequestsShouldUseCustomEndpointWhenDefinedInMobkoiExtension() {
         // given