renew
abstract suspend fun renew(group: String, partitions: Collection<Int>, owner: String, ttl: Duration): List<Lease>
Extends to ttl from now each live lease owner holds on one of partitions, and returns them; a partition owner no longer holds is left out. A node renews all its leases with one call each round, so a backend renews them in one round trip where it can; a failure fails the whole call.