Stop depending the bossbar metadata rewriter on the bukkit api (#391)

* Don't depend the bossbar metadata rewriter on the bukkit api

* Rename field

src/main/java/us/myles/ViaVersion/api/boss/BossBar.java

@@ -69,6 +69,14 @@ public interface BossBar {
      */
     BossBar addPlayer(Player player);
 
+    /**
+     * Show the bossbar to a player (uuid)
+     *
+     * @param player uuid of the player
+     * @return the BossBar instance
+     */
+    BossBar addPlayer(UUID player);
+
     /**
      * add multiple players
      *

src/main/java/us/myles/ViaVersion/boss/ViaBossBar.java

@@ -78,10 +78,15 @@ public class ViaBossBar implements BossBar {
 
     @Override
     public BossBar addPlayer(@NonNull Player player) {
-        if (!players.contains(player.getUniqueId())) {
+        return addPlayer(player.getUniqueId());
-            players.add(player.getUniqueId());
+    }
+
+    @Override
+    public BossBar addPlayer(UUID player) {
+        if (!players.contains(player)) {
+            players.add(player);
             if (visible)
-                sendPacket(player.getUniqueId(), getPacket(UpdateAction.ADD));
+                sendPacket(player, getPacket(UpdateAction.ADD));
         }
         return this;
     }

src/main/java/us/myles/ViaVersion/protocols/protocol1_9to1_8/storage/EntityTracker.java

@@ -5,10 +5,8 @@ import com.google.common.cache.CacheBuilder;
 import io.netty.buffer.ByteBuf;
 import lombok.Getter;
 import lombok.Setter;
-import org.bukkit.Bukkit;
 import org.bukkit.Material;
 import org.bukkit.entity.EntityType;
-import org.bukkit.entity.Player;
 import us.myles.ViaVersion.ViaVersionPlugin;
 import us.myles.ViaVersion.api.PacketWrapper;
 import us.myles.ViaVersion.api.ViaVersion;
@@ -179,7 +177,7 @@ public class EntityTracker extends StoredObject {
                     }
                 }
             }
-            Player player = Bukkit.getPlayer(getUser().get(ProtocolInfo.class).getUuid());
+            UUID uuid = getUser().get(ProtocolInfo.class).getUuid();
             // Boss bar
             if (((ViaVersionPlugin) ViaVersion.getInstance()).isBossbarPatch()) {
                 if (type == EntityType.ENDER_DRAGON || type == EntityType.WITHER) {
@@ -190,7 +188,7 @@ public class EntityTracker extends StoredObject {
                         if (bar == null) {
                             bar = ViaVersion.getInstance().createBossBar(title, BossColor.PINK, BossStyle.SOLID);
                             bossBarMap.put(entityID, bar);
-                            bar.addPlayer(player);
+                            bar.addPlayer(uuid);
                             bar.show();
                         } else {
                             bar.setTitle(title);
@@ -204,7 +202,7 @@ public class EntityTracker extends StoredObject {
                             String title = type == EntityType.ENDER_DRAGON ? "Ender Dragon" : "Wither";
                             bar = ViaVersion.getInstance().createBossBar(title, health, BossColor.PINK, BossStyle.SOLID);
                             bossBarMap.put(entityID, bar);
-                            bar.addPlayer(player);
+                            bar.addPlayer(uuid);
                             bar.show();
                         } else {
                             bar.setHealth(health);