V4.0.3

• Make closing the Store more robust. In addition to transactions, it also waits for ongoing queries. This is just an
  additional safety net. Your apps should still make sure to finish all Store operations, like queries, before closing it.
• Flex properties support null map and list values.
• Some minor vector search performance improvements.

Sync

• Fix a serious regression, please update as soon as possible.
• Add new options, notably for cluster configuration, when building SyncServer. Improve documentation.
  Deprecate the old peer options in favor of the new cluster options.
• Add SyncHybrid, a combination of a Sync client and a Sync server. It can be used in local cluster setups, in
  which a "hybrid" functions as a client & cluster peer (server).