The index is being created, and cannot be used by queries.
There is an active long-running operation for the index.
The index is updated when writing an entity.
Some index data may exist.
Deleting
The index is being deleted, and cannot be used by queries.
There is an active long-running operation for the index.
The index is not updated when writing an entity.
Some index data may exist.
Error
The index was being created or deleted, but something went wrong.
The index cannot by used by queries.
There is no active long-running operation for the index,
and the most recently finished long-running operation failed.
The index is not updated when writing an entity.
Some index data may exist.
Ready
The index is ready to be used.
The index is updated when writing an entity.
The index is fully populated from all stored entities it applies to.
