RSS service

[Gomez]

To implement a RSS tile (plone/volto#291) we need rest endpoints to bypass CORS problems. A POC could look like this:

A manager could post a rss url to this endpoint:

    <plone:service
      method="POST"
      name="@rss-feed"
      for="Products.CMFCore.interfaces.ISiteRoot"
      factory=".post.RssPost"
      permission="cmf.ManagePortal"
    />

Anonymous user cloud get rss feeds from this endpoint:

    <plone:service
      method="GET"
      name="@rss-feeds"
      for="Products.CMFCore.interfaces.ISiteRoot"
      factory=".get.RssFeedsGet"
      permission="zope2.View"
    />

In a first version it would be ok to just save the data in memory. On restart of the server, the first request would poll the RSS. Saving it persistent would be difficult.

For now we decided to postpone the rss tile. To much work and security issues to get it into core/restapi.