Cannot deal with deleted resources?

[crantila]

I have to double check this, but I'm pretty sure that, because of how things are exported from Drupal, HolyOrders will never find out about deleted resources. Furthermore, even if we did find out, there's no machinery to deal with it at the moment.

While I don't think deleting will be that important as itself, it is also a strategy for dealing with resources that change ID, which would otherwise appear in Solr in multiples.

[crantila]

I managed to get a "view" working that exports data about deleted content nodes (deleted_records). The data look something like this:

<deletions>
  <deletion>
    <timestamp>2016-07-07T18:29:38+07:00</timestamp>
    <location>http://cantus.uwaterloo.ca/node/663321/delete</location>
    <type>chant</type>
  </deletion>
</deletions>

From this, it's possible to figure out which node to remove in Solr.

We can record the time of the most recent round of deletions in the database. I couldn't find a reasonable way to paginate by date, but the output is sorted with newest events first, so as soon as we find a <timestamp> older than our most recent deletion update, we can stop.

I'm absolutely sure this could be overwhelmed if there are too many deletions within the log's time period. I don't know what to do about that yet.