docs: public Future<AuthenticationResult> acquireToken(final String resource,
              final UserAssertion userAssertion, final ClientCredential credential,
              final AuthenticationCallback callback) {
  
          this.validateOnBehalfOfRequestInput(resource, userAssertion, credential, true);
          final ClientAuthentication clientAuth = new ClientSecretPost(
                  new ClientID(credential.getClientId()), new Secret(
                  credential.getClientSecret()));
          return acquireTokenOnBehalfOf(resource, userAssertion, clientAuth, callback);
      }