Function embedding 

pub fn embedding(reviews: Reviews, grants: &[&str], limits: Limits) -> Embedding

Registers reviews, grants grants, imposes limits, and watches the boundary.

Registering a module does not grant it: a capability missing from grants makes every call into the module a refusal, which is one of the cases the tests beside this file pin.

limits is what bounds the session: it is installed on the registry before anything runs, and every invocation the session makes spends out of the one budget. That is what an application wants for the limits that are about the process rather than about a request.

It is no longer the only choice, which it was when this example was written. A limit that belongs to one request is what a rule engine actually wants – a rule package is somebody else’s code, and an application running one wants to be told when a rule loops rather than to stop serving – and Session::evaluate_within is that: the same compiled package, the same Vm, and a Budget per invocation. Issue #152 was the gap, and examples/rules/README.md says what it used to cost.

Pass Limits::default here for a session that is bounded per request and not otherwise, which is what the cases beside this file do.