3.0.0b0

BREAKING

The 3.x series of releases will bring CastleCMS into compatibility with
ElasticSearch 7. Practically, this means primarily updating 3 packages:

• castle.cms >= 3
• collective.elasticsearch >= 4
• elasticsearch >= 7, <= 7.6

The elasticsearch package is restricted between 7 and 7.6 primarily due to
the restriction from collective.elasticsearch -- this is expected to be
updated at some point, but not for the initial release of castle.cms 3.x.

For migration, it is recommended that you setup a new ES cluster, update
site configurations to point at the new cluster, then do the "Convert" and
"Rebuild" actions in the ElasticSearch control panel.

This will not migrate your audit log, if enabled. To migrate the audit log,
use the castle/cms/_scripts/export-audit-log.py script to dump the old
audit log into a CSV file, and then use the castle/cms/_scripts/import-audit-log.py
script to import the CSV file into the new cluster.