default void scheduleBatch(Stream<SchedulableInstance<?>> schedulableInstances) {
    StreamUtils.chunkStream(schedulableInstances, DEFAULT_BATCH_SIZE).forEach(this::scheduleBatch);
  }
Schedule a batch of executions. If any of the executions already exists, the scheduling will
fail and an exception will be thrown.

@param schedulableInstances Task-instances with individual execution-times
@see com.github.kagkarlsson.scheduler.task.SchedulableInstance
db-scheduler/src/main/java/com/github/kagkarlsson/scheduler/SchedulerClient.java