Support multiple TRACE_ID in SharedRefDbExceptionHook

Adapt the SharedRefDbExceptionHook to the ExceptionHook
signature amended with Iebfc5301a2ad.

Change-Id: I0f20d070dda5a140a27da15d8b8e5685236c2ad9

src/main/java/com/gerritforge/gerrit/globalrefdb/validation/SharedRefDbExceptionHook.java

diff --git a/src/main/java/com/gerritforge/gerrit/globalrefdb/validation/SharedRefDbExceptionHook.java b/src/main/java/com/gerritforge/gerrit/globalrefdb/validation/SharedRefDbExceptionHook.java
index a7f2740..e0495d5 100644
--- a/src/main/java/com/gerritforge/gerrit/globalrefdb/validation/SharedRefDbExceptionHook.java
+++ b/src/main/java/com/gerritforge/gerrit/globalrefdb/validation/SharedRefDbExceptionHook.java
@@ -16,7 +16,7 @@
 
 import com.gerritforge.gerrit.globalrefdb.GlobalRefDbLockException;
 import com.google.common.collect.ImmutableList;
-import com.google.gerrit.common.Nullable;
+import com.google.common.collect.ImmutableSet;
 import com.google.gerrit.server.ExceptionHook;
 import java.util.Optional;
 
@@ -36,12 +36,14 @@
   }
 
   @Override
-  public ImmutableList<String> getUserMessages(Throwable throwable, @Nullable String traceId) {
+  public ImmutableList<String> getUserMessages(Throwable throwable, ImmutableSet<String> traceIds) {
     if (throwable instanceof GlobalRefDbLockException) {
       ImmutableList.Builder<String> builder = new ImmutableList.Builder<>();
       builder.add(throwable.getMessage());
-      if (traceId != null && !traceId.isBlank()) {
-        builder.add(String.format("Trace ID: %s", traceId));
+      for (String traceId : traceIds) {
+        if (traceId != null && !traceId.isBlank()) {
+          builder.add(String.format("Trace ID: %s", traceId));
+        }
       }
       return builder.build();
     }