feat: make inner client to interact w/ the API public

Author: rhamzeh

src/main/java/dev/openfga/sdk/api/client/OpenFgaClient.java

@@ -33,7 +33,7 @@
 public class OpenFgaClient {
     private final ApiClient apiClient;
     private ClientConfiguration configuration;
-    private OpenFgaApi api;
+    public OpenFgaApi api;
 
     private static final String CLIENT_BULK_REQUEST_ID_HEADER = "X-OpenFGA-Client-Bulk-Request-Id";
     private static final String CLIENT_METHOD_HEADER = "X-OpenFGA-Client-Method";