Fix DamageSource API (#10307)

Uses the correct entity in the EntityDamageByEntity event
Returns the correct entity for API's DamageSource#getCausingEntity

patches/api/Fix-DamageSource-API.patch

@@ -0,0 +1,31 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Jake Potrebic <jake.m.potrebic@gmail.com>
+Date: Sat, 16 Mar 2024 11:21:14 -0700
+Subject: [PATCH] Fix DamageSource API
+
+
+diff --git a/src/main/java/org/bukkit/event/entity/EntityDamageByEntityEvent.java b/src/main/java/org/bukkit/event/entity/EntityDamageByEntityEvent.java
+index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
+--- a/src/main/java/org/bukkit/event/entity/EntityDamageByEntityEvent.java
++++ b/src/main/java/org/bukkit/event/entity/EntityDamageByEntityEvent.java
+@@ -0,0 +0,0 @@ public class EntityDamageByEntityEvent extends EntityDamageEvent {
+     }
+     // Paper end
+ 
++    // Paper start
++    /**
++     * {@inheritDoc}
++     * <p>
++     * The {@link DamageSource#getDirectEntity()} may be different from the {@link #getDamager()}
++     * if the Minecraft damage source did not originally include an damager entity, but one was included
++     * for this event {@link #getDamager()}.
++     */
++    @Override
++    public @NotNull DamageSource getDamageSource() {
++        return super.getDamageSource();
++    }
++    // Paper end
++
+     /**
+      * Returns the entity that damaged the defender.
+      *