Streamline SA publishing

On Wednesdays, security advisories go from SA draft nodes on security.drupal.org to sa nodes on www.drupal.org. This is done with some copy/paste and is tedious. Some things, like the project field, work much nicer when auto-filled (we have a query parameter for that https://www.drupal.org/node/add/sa?field_project=185188).

We can either:

• Open up POST to RestWS from the internal network, so security.drupal.org can push the content in. Needs testing to figure out how well this works, no one has volunteered to do this for other potential robots wanting to post content.
• Set up the node add sa form to handle population of the fields more client-side — more URL query parameters, or allow some sort of cross-site POSTing.