<!-- For Security Vulnerabilities, please use https://pivotal.io/security#reporting --> ### Summary * Add a `public void setWebClient(WebClient webClient)` method to [WebClientReactiveClientCredentialsTokenResponseClient](https://github.com/spring-projects/spring-security/blob/5.1.1.RELEASE/oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/endpoint/WebClientReactiveClientCredentialsTokenResponseClient.java). * Ensure that the value passed in cannot be null. * Add a [test](https://github.com/spring-projects/spring-security/blob/5.1.1.RELEASE/oauth2/oauth2-client/src/test/java/org/springframework/security/oauth2/client/endpoint/WebClientReactiveClientCredentialsTokenResponseClientTests.java) to ensure that `null` cannot be passed in * Add a test to ensure that a custom `WebClient` is used if set