Namespace Replication between OpenBao clusters

Problem

When running multiple OpenBao clusters, we may need to replicate shared secrets from one cluster to another. Certainly, secrets which are needed locally only must not be replicated for security reasons.

For example, customers may run one OpenBao cluster in region A and another OpenBao cluster in region B. Shared secrets which are needed in both regions must be replicated from A to B (or vice versa). We may keep shared secrets in a separate namespace.

Feature Request

Thus, we propose replication per namespace. Namespaces containing shared secrets get replicated, while namespaces containing local secrets don't get replicated. Note that replication between multiple OpenBao clusters cannot be implemented on storage level, because each OpenBao cluster has its own storage.