Merge chr name + id wrappers into new CharacterIdentity record

src/main/java/model/CharacterIdentity.java

@@ -0,0 +1,9 @@
+package model;
+
+public record CharacterIdentity(String name, int id) {
+    public CharacterIdentity {
+        if (name == null) {
+            throw new IllegalArgumentException("Character name must not be null");
+        }
+    }
+}