[BUG] `multitenant` incompatible with NATS

[mikenikles]

When I set WADM_MULTITENANT=true, the server crashes with the following error message:

Error { kind: JetStream(Error { code: 500, err_code: ErrorCode(10052), description: Some("subjects that overlap with jetstream api require no-ack to be true") }), source: None }

I narrowed it down to this line in https://github.com/nats-io/nats-server.

In wadm, this code block causes the issue:

let topic_prefix = if multitenant {
    format!("*.{prefix}")
} else {
    prefix.clone()
};

To resolve this, we need to prefix multitenant topics with an additional value to prevent it from clashing with $JS.>. Either a hardcoded value or a configurable one would do.

For example:

let topic_prefix = if multitenant {
    format!("multitenant.*.{prefix}")
} else {
    prefix.clone()
};

This would also require changes to how NATS account imports/exports are set up in https://github.com/wasmCloud/wadm/blob/main/tests/nats/nats-test.conf.

FWIW, this started to break in summer of 2024 with this code change.