fix(server): fix crash when there is no rating events yet (#564)

Author: fushar

judgels-backends/judgels-server-api/src/main/java/judgels/uriel/api/contest/rating/ContestRatingChanges.java

@@ -7,7 +7,7 @@
 import org.immutables.value.Value;
 
 @Value.Immutable
-@JsonDeserialize(as = ImmutableContestRating.class)
+@JsonDeserialize(as = ImmutableContestRatingChanges.class)
 public interface ContestRatingChanges {
     Map<String, UserRating> getRatingsMap();
     Map<String, Profile> getProfilesMap();

judgels-backends/judgels-server-app/src/integTest/java/judgels/uriel/api/ContestRatingApiIntegrationTests.java

@@ -0,0 +1,16 @@
+package judgels.uriel.api;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import judgels.uriel.ContestRatingClient;
+import org.junit.jupiter.api.Test;
+
+class ContestRatingApiIntegrationTests extends BaseUrielApiIntegrationTests {
+    private final ContestRatingClient ratingClient = createClient(ContestRatingClient.class);
+
+    @Test
+    void get_pending_ratings() {
+        assertThat(ratingClient.getContestsPendingRating(superadminToken).getData())
+                .isEmpty();
+    }
+}

judgels-backends/judgels-server-app/src/main/java/judgels/uriel/contest/rating/ContestRatingResource.java

@@ -62,7 +62,7 @@ public ContestsPendingRatingResponse getContestsPendingRating(@HeaderParam(AUTHO
         checkAllowed(contestRoleChecker.canAdminister(actorJid));
 
         Optional<RatingEvent> latestEvent = jophielClient.getLatestRatingEvent();
-        Instant latestTime = latestEvent.isPresent() ? latestEvent.get().getTime() : Instant.MIN;
+        Instant latestTime = latestEvent.isPresent() ? latestEvent.get().getTime() : Instant.EPOCH;
 
         List<Contest> contests = contestStore.getPublicContestsAfter(latestTime);
         Map<String, ContestRatingChanges> ratingChangesMap = contests.stream()

judgels-backends/judgels-server-feign/src/main/java/judgels/uriel/ContestRatingClient.java

@@ -0,0 +1,12 @@
+package judgels.uriel;
+
+import feign.Headers;
+import feign.Param;
+import feign.RequestLine;
+import judgels.uriel.api.contest.rating.ContestsPendingRatingResponse;
+
+public interface ContestRatingClient {
+    @RequestLine("GET /api/v2/contest-rating/pending")
+    @Headers("Authorization: Bearer {token}")
+    ContestsPendingRatingResponse getContestsPendingRating(@Param("token") String token);
+}