feat(model): World.combinations field + backward-compatible constructors

Semesterprojekt/src/test/java/thb/jeanluc/adventure/model/WorldCombinationsTest.java

@@ -0,0 +1,29 @@
+package thb.jeanluc.adventure.model;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+import java.util.Map;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class WorldCombinationsTest {
+
+    @Test
+    void legacyConstructorsDefaultToEmptyCombinations() {
+        World w5 = new World(Map.of(), Map.of(), Map.of(), "t", "w");
+        World w6 = new World(Map.of(), Map.of(), Map.of(), "t", "w", Map.of());
+        World w7 = new World(Map.of(), Map.of(), Map.of(), "t", "w", Map.of(), List.of());
+        assertThat(w5.getCombinations()).isEmpty();
+        assertThat(w6.getCombinations()).isEmpty();
+        assertThat(w7.getCombinations()).isEmpty();
+    }
+
+    @Test
+    void fullConstructorStoresCombinations() {
+        Combination c = new Combination("a", "b", List.of(), List.of(), null, List.of(), "r", null);
+        World w = new World(Map.of(), Map.of(), Map.of(), "t", "w",
+                Map.of(), List.of(), Map.of(c.key(), c));
+        assertThat(w.getCombinations()).containsKey("a|b");
+    }
+}