* new datetime fields added to library component serializer: created,
  modified, and last_published
* new datetime fields are stored in Meilisearch as POSIX timestamps for
  sorting
* Meilisearch search ranking updated to allow sorting by display_name or
  these new datetime fields
* Updates tests to verify these new properties and client settings

* Instead of using `latest.modified` (which always queries the
  database), use `draft.latest`
* However, we have to increase the query count by 1 query per block,
  because the published_at date can only be found in the publish log,
  which must be fetched individually for each block.

…t-dates

…t-dates