* <p>Usage example:
 * <pre>
 * {@code
 * Map<String, String> params = new HashMap<>();
 * params.put("token_url", "http://example.com/token");
 * params.put("login_url", "http://example.com/login");
 * Hc5FormScheme formScheme = new Hc5FormScheme(params);
 * formScheme.authenticate(credentials, executor);
 * }
 * </pre>
 *
 * <p>Parameters:
 * <ul>
 * <li>ENCODING - The character encoding to use for request parameters.</li>