Client

The client now uses elastic-transport-go dependency which lives in its own repository.
With the knewly extracted transport, the retryOnTimeout has been replaced with a retryOnError callback. This allows to select more finely which error should be retried by the client.
BulkIndexerItem Body field is now an io.ReadSeeker allowing reread without increasing memory consumption.
BulkIndexerItem know correctly uses the routing property instead of the deprecated _routing.

API