Refactor damage source checking and restructure player management

The source of damage detection for PvP interactions has been updated to improve accuracy and flexibility. A 'Target' sub-class has been implemented in the PlayerManager class, removing the need for a separate DamageCheck class. The PlayerManager class was also moved to the 'data' package. Distribution of feedback messages has been simplified using the new DamageCheckResult class.

src/main/java/me/youhavetrouble/preventstabby/data/DamageCheckResult.java

@@ -0,0 +1,41 @@
+package me.youhavetrouble.preventstabby.data;
+
+import javax.annotation.Nullable;
+import java.util.UUID;
+
+/**
+ * @param ableToDamage  Result of the damage check
+ * @param feedbackForAttacker Feedback to send to the attacker
+ * @param feedbackForVictim Feedback to send to the victim
+ * @param attackerId UUID of attacker player
+ * @param victimId UUID of victim player
+ */
+public record DamageCheckResult(
+        boolean ableToDamage,
+        @Nullable UUID attackerId,
+        @Nullable UUID victimId,
+        @Nullable String feedbackForAttacker,
+        @Nullable String feedbackForVictim
+) {
+
+    public static DamageCheckResult positive() {
+        return new DamageCheckResult(
+                true,
+                null,
+                null,
+                null,
+                null
+        );
+    }
+
+    public static DamageCheckResult positive(UUID attackerId, UUID victimId) {
+        return new DamageCheckResult(
+                true,
+                attackerId,
+                victimId,
+                null,
+                null
+        );
+    }
+
+}