update samples

samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/ApiClient.java

@@ -123,6 +123,16 @@ public class ApiClient {
     return objectMapper;
   }
 
+  private RequestInterceptor buildOauthRequestInterceptor(OAuthFlow flow, String authorizationUrl, String tokenUrl, String scopes) {
+    switch (flow) {
+      case password:
+        return new OauthPasswordGrant(tokenUrl, scopes);
+      case application:
+        return new OauthClientCredentialsGrant(authorizationUrl, tokenUrl, scopes);
+      default:
+        throw new RuntimeException("Oauth flow \"" + flow + "\" is not implemented");
+    }
+  }
 
   public ObjectMapper getObjectMapper(){
     return objectMapper;