Add Vault block API

paper-api/src/main/java/org/bukkit/block/Vault.java

@@ -144,10 +144,10 @@ public interface Vault extends TileState {
      * @apiNote Vaults will only periodically scan for nearby players, so this collection may take until the next {@link #getNextStateUpdateTime() update time} to update
      * upon a player entering its range.
      *
-     * @return An unmodifiable list of connected player uuids.
+     * @return An unmodifiable set of connected player uuids.
      */
     @Unmodifiable
-    Collection<UUID> getConnectedPlayers();
+    Set<UUID> getConnectedPlayers();
 
     /**
      * Gets the item currently being displayed inside this vault. Displayed items will automatically cycle between random items from the {@link #getDisplayedLootTable()}

paper-server/src/main/java/org/bukkit/craftbukkit/block/CraftVault.java

@@ -15,7 +15,6 @@
 import org.jetbrains.annotations.Unmodifiable;
 import org.jspecify.annotations.NullMarked;
 import org.jspecify.annotations.Nullable;
-import java.util.Collection;
 import java.util.Optional;
 import java.util.Set;
 import java.util.UUID;
@@ -136,7 +135,7 @@ public boolean removeRewardedPlayer(final UUID playerUUID) {
     }
 
     @Override
-    public @Unmodifiable Collection<UUID> getConnectedPlayers() {
+    public @Unmodifiable Set<UUID> getConnectedPlayers() {
         return ImmutableSet.copyOf(this.getSnapshot().getSharedData().getConnectedPlayers());
     }