Fix repository leak in enhanced client

lib/src/main/java/growthbook/sdk/java/multiusermode/GrowthBookClient.java

@@ -184,6 +184,14 @@ public void subscribe(ExperimentRunCallback callback) {
         this.callbacks.add(callback);
     }
 
+    public void shutdown() {
+      if (repository != null) {
+        repository.shutdown();
+        repository = null;
+        log.info("Repository shut down");
+      }
+    }
+
     private <ValueType> void fireSubscriptions(Experiment<ValueType> experiment, ExperimentResult<ValueType> result) {
         String key = experiment.getKey();
         // If assigned variation has changed, fire subscriptions

lib/src/test/java/growthbook/sdk/java/multiusermode/GrowthBookClientTest.java

@@ -108,6 +108,44 @@ void test_initialization_withFailedFeatureFetch() throws FeatureFetchException {
         }
     }
 
+  @Test
+  void test_shutdown_withANonInitializedClient() {
+    mockRepository = createMockRepository();
+    mockBuilder = createMockBuilder(mockRepository);
+    FeatureRefreshCallback mockCallback = mock(FeatureRefreshCallback.class);
+
+    try (MockedStatic<GBFeaturesRepository> mockedStatic = mockStatic(GBFeaturesRepository.class)) {
+      mockedStatic.when(GBFeaturesRepository::builder).thenReturn(mockBuilder);
+
+      Options options = createDefaultOptions(mockCallback);
+
+      GrowthBookClient client = new GrowthBookClient(options);
+
+      client.shutdown();
+
+      verify(mockRepository, never()).shutdown();
+    }
+  }
+  @Test
+  void test_shutdown_withAnInitializedClient() {
+    mockRepository = createMockRepository();
+    mockBuilder = createMockBuilder(mockRepository);
+    FeatureRefreshCallback mockCallback = mock(FeatureRefreshCallback.class);
+
+    try (MockedStatic<GBFeaturesRepository> mockedStatic = mockStatic(GBFeaturesRepository.class)) {
+      mockedStatic.when(GBFeaturesRepository::builder).thenReturn(mockBuilder);
+
+      Options options = createDefaultOptions(mockCallback);
+
+      GrowthBookClient client = new GrowthBookClient(options);
+      client.initialize();
+
+      client.shutdown();
+
+      verify(mockRepository).shutdown();
+    }
+  }
+
     //@Test
     void test_evalFeature_withUserContext() {
         String attributes = "{ \"user_group\": \"subscriber\", \"beta_users\": true }";
@@ -167,4 +205,4 @@ private Options createDefaultOptions(FeatureRefreshCallback callback) {
                 .featureRefreshCallback(callback)
                 .build();
     }
-}
+}