Auth0Utils.java

    /**
     * <p>Create a {@link WebClient} using OAuth2 (Auth0) authentication (MTM)</p>
     *
     * @param clientRegistrationRepository The repository of client registrations
     * @param authorizedClientRepository   The repository of authorized clients
     * @param clientRegistrationId         The Client Registration Id to use to get the authentication info (clientId, clientSecret, scope...)
     * @param url                          The base URL of REST Service this client is interacting with
     * @param audience                     The audience to pass to the authentication request sent to Auth0
     * @return a {@link WebClient} instance preconfigured to access to the remote service
     * @since 1.1.0
     */
    @Nonnull
    public static WebClient createWebClient(@Nonnull ClientRegistrationRepository clientRegistrationRepository,
                                            @Nonnull OAuth2AuthorizedClientRepository authorizedClientRepository,
                                            @Nonnull String clientRegistrationId,
                                            @Nonnull String url,
                                            @Nonnull String audience) {
        Converter<OAuth2ClientCredentialsGrantRequest, RequestEntity<?>> customRequestEntityConverter =
            new Auth0ClientCredentialsGrantRequestEntityConverter(audience);

        DefaultClientCredentialsTokenResponseClient clientCredentialsTokenResponseClient =
            new DefaultClientCredentialsTokenResponseClient();
        clientCredentialsTokenResponseClient.setRequestEntityConverter(customRequestEntityConverter);

        ClientCredentialsOAuth2AuthorizedClientProvider clientCredentialsOAuth2AuthorizedClientProvider =
            new ClientCredentialsOAuth2AuthorizedClientProvider();
        clientCredentialsOAuth2AuthorizedClientProvider
            .setAccessTokenResponseClient(clientCredentialsTokenResponseClient);

        DefaultOAuth2AuthorizedClientManager authorizedClientManager =
            new DefaultOAuth2AuthorizedClientManager(clientRegistrationRepository, authorizedClientRepository);
        authorizedClientManager.setAuthorizedClientProvider(clientCredentialsOAuth2AuthorizedClientProvider);

        ServletOAuth2AuthorizedClientExchangeFilterFunction oauth2Client =
            new ServletOAuth2AuthorizedClientExchangeFilterFunction(authorizedClientManager);
        oauth2Client.setDefaultClientRegistrationId(clientRegistrationId);

        return WebClient.builder()
            .baseUrl(url)
            .apply(oauth2Client.oauth2Configuration())
            .build();
    }