driver: add couchbase support

[Dentrax]

It'd be fun and easy to implement. If the maintainers say OK, it's ready to go.

Library is: https://github.com/couchbase/gocb

Dropping the idea here as good-first-issue so we don't forget.

[brandond]

I think this would probably be fairly non-trivial to implement this, as couchbase is itself a key-value store and isn't a good fit for the row-based semantics that Kine's sql backends expect. It might be possible to implement a more low-level adapter, similar to what was done for NATS Jetstream, but it would probably have to come from someone with a better understanding of couchbase's document storage model than our team currently has available.

in short - I don't think we're going to do it ourselves, but we'd welcome a PR from the community!