[Feature Request] Add support for retention and mode for S3 buckets that has S3 Object lock enabled

[mrlindblom]

When S3 Object lock a default policy can be configured for each bucket, however each each Put Object request can have its own retention period and retention mode setting.

For recurring backups it would be nice to have retention period equal to what is configure in the schedule and retention count.
A new field for retention mode would be need.

Documentation
https://docs.aws.amazon.com/AmazonS3/latest/userguide/object-lock.html#object-lock-overview

PutObjectRetention example
https://docs.aws.amazon.com/code-library/latest/ug/go_2_s3_code_examples.html