docs: protected Authentication extractCredentials(HttpServletRequest request) {
  		String grantType = request.getParameter("grant_type");
  		if (grantType != null && grantType.equals("password")) {
  			UsernamePasswordAuthenticationToken result = new UsernamePasswordAuthenticationToken(
  					request.getParameter("username"), request.getParameter("password"));
  			result.setDetails(authenticationDetailsSource.buildDetails(request));
  			return result;
  		}
  		return null;
  	}