S3 storage for Backup and Restore

The OpenBao operator implements the requirer side of the S3 interface, enabling it to integrate with any charm that implements the provider side of this interface.

The OpenBao operator obtains the necessary information to connect to S3 storage through the S3 relation interface.

S3-integrator charm can also be used to integrate OpenBao with S3 storage if the storage itself does not support the S3 charm relation interface.