Add Rc to Arc feature in async and multithread context

[azoyan]

Is it possible to add feature to replace Rc in inner structures to Arc to use in async context?

pub struct RateLimitBodyJsonPath {
    pub jsonpath: Vec<RsonpathEngine>
}

error[E0277]: `Rc<StringPattern>` cannot be shared between threads safely
   --> core/src/rule/mod.rs:339:21
    |
339 | /                     tokio::spawn(async move {
340 | |                         let mut guard = RULES.write().await;
341 | |                         guard.remove(tenant_clone.as_str());
342 | |                     });
    | |______________________^ `Rc<StringPattern>` cannot be shared between threads safely
    |
    = help: within `[(Rc<StringPattern>, rsonpath::automaton::State); 2]`, the trait `Sync` is not implemented for `Rc<StringPattern>`, which is required by `{async block@core/src/rule/mod.rs:339:34: 339:44}: Send`
    = note: required because it appears within the type `(Rc<StringPattern>, rsonpath::automaton::State)`
    = note: required because it appears within the type `[(Rc<StringPattern>, rsonpath::automaton::State); 2]`
    = note: required for `smallvec::SmallVecData<[(Rc<StringPattern>, rsonpath::automaton::State); 2]>` to implement `Sync`

[github-actions]

Tagging @V0ldek for notifications

[V0ldek]

It's possible, but after the holiday break 😄

For now as a workaround you can make it Send and Sync with a wrapper and unsafe

struct RsonpathEngineWrap(RsonpathEngine);

unsafe impl Send for RsonpathEngineWrap {}
unsafe impl Sync for RsonpathEngineWrap {}

This is safe because

1. RsonpathEngine is not Clone
2. We never clone the Rcs inside the Automaton after construction and always pass the strings by reference.

In other words the Rcs are never cloned after the engine is built.