BulkIndexer throw error when es.Client not provided ?

[mayankvaid88]

Currently, NewBulkInderxer function creates a elasticsearch.Client with default ES URL=localhost:9200 in case if it is not provided by the consumer. In most of the PROD ready applications ES Url address would be different from the default address and it makes sense to give a feedback in terms of error rather than creating it to default. This will help in getting an early feedback to the consumer to course correct it.
https://github.com/elastic/go-elasticsearch/blob/main/esutil/bulk_indexer.go#L190