static AccessTokenRequest ofClientCredentials(ClientAuthentication clientAuthentication,
                                                  List<String> scopes) {
        requireNonNull(clientAuthentication, "clientAuthentication");
        requireNonNull(scopes, "scopes");
        return new ClientCredentialsAccessTokenRequest(clientAuthentication, scopes);
    }
Creates a new {@link AccessTokenRequest} that is used to request an access token using the client
credentials and the scopes, as per
<a href="https://datatracker.ietf.org/doc/html/rfc6749#section-4.4">RFC 6749, Section 4.4</a>.
oauth2/src/main/java/com/linecorp/armeria/client/auth/oauth2/AccessTokenRequest.java