code: public Credentials<UserPasswordToken> extractCredentials(final Request request) {
      final String basicAuthHeader = request.getHeader(BASIC_AUTHORIZATION_HEADER);
      if (StringUtils.isNotBlank(basicAuthHeader) && basicAuthHeader.startsWith(BASIC_PREFIX)) {
        return extractCredentials(basicAuthHeader);
      } else {
        return null;
      }
    }
docs: <p>
  Extracts the credentials from the request by obtaining the Authorization header's value
  and parsing it. Everything after the &quot;Basic&quot; prefix will be Base64 decoded and returns.
  </p>
  Examples:<br>
  <pre>
  Authorization Header            Result
  ---------------------------------------------
  null                            null
  ""                              null
  "Basic unencoded_string"        null
  "Basic dXNlcjpwYXNzd29yZA=="    {@code new UsernamePasswordTuple("user", "password"}
  </pre>
  
  @return the decoded credentials, or null if any error occured