issue2550949: Rate limit password guesses/login attempts. Generic rate limit mechanism added. Deployed for web page logins. Default is 3 login attempts/minute for a user. After which one login attempt every 20 seconds can be done. Uses gcra algorithm so all I need to store is a username and timestamp in the one time key database. This does mean I don't have a list of all failed login attempts as part of the rate limiter. Set up config setting as well so admin can tune the rate. Maybe 1 every 10 seconds is ok at a site with poor typists who need 6 attempts to get the password right 8-). The gcra method can also be used to limit the rest and xmlrpc interfaces if needed. The mechanism I added also supplies a status method that calculates the expected values for http headers returned as part of rate limiting. Also tests added to test all code paths I hope.

<!-- dollarId: issue.item,v 1.4 2001/08/03 01:19:43 richard Exp dollar-->
<tal:block metal:use-macro="templates/page/macros/icing">
  <title metal:fill-slot="head_title">
  Item Not Found
  </title>
  <tal:block metal:fill-slot="body_title">
  Item Not Found
  </tal:block>

<td class="content" metal:fill-slot="content">
    There is no <span tal:content="context/_classname" /> with id
    <span tal:content="context/id"/>
</td>
</tal:block>