feat: Async retriever

[Stranger6667]

Resolves #385

let validator = jsonschema::async_validator_for(&schema).await?;

[codecov]

Codecov Report

Attention: Patch coverage is 96.38672% with 37 lines in your changes missing coverage. Please review.

Project coverage is 85.99%. Comparing base (6a529dd) to head (e2c36be).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
crates/jsonschema/src/options.rs	83.33%	18 Missing ⚠️
crates/jsonschema-py/src/lib.rs	0.00%	10 Missing ⚠️
crates/jsonschema-py/src/retriever.rs	0.00%	4 Missing ⚠️
crates/jsonschema-py/src/registry.rs	0.00%	2 Missing ⚠️
crates/jsonschema/src/compiler.rs	96.87%	2 Missing ⚠️
crates/jsonschema/src/retriever.rs	99.36%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #703      +/-   ##
==========================================
+ Coverage   85.31%   85.99%   +0.67%     
==========================================
  Files          94       94              
  Lines       14448    15220     +772     
==========================================
+ Hits        12327    13089     +762     
- Misses       2121     2131      +10     

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[codspeed-hq]

CodSpeed Performance Report

Merging #703 will not alter performance

_{Comparing dd/async-retrieve (e2c36be) with master (6a529dd)}

Summary

✅ 47 untouched benchmarks

[Stranger6667]

Tagging @uncenter @gadomski because of your recent PRs (in taplo and stac-rs respectively) which may benefit from this feature in jsonschema.

This is a very early iteration for async retrieval of external schemas, but it works (the original message with an example above)! If you have any feedback on the API or think that I've missed something here, please, let me know :)

I plan to work more on this feature so it covers your use cases and has the least amount of rough edges in terms of usability and ergonomics.

[Stranger6667]

With the latest update, the following would work for the simplest case:

let validator = jsonschema::async_validator_for(&schema).await?;

And custom non-blocking retrievers are also possible:

use serde_json::{Value, json};
use jsonschema::{Draft, AsyncRetrieve, Uri};

// Custom async retriever
struct MyRetriever;

#[async_trait::async_trait]
impl AsyncRetrieve for MyRetriever {
    async fn retrieve(&self, uri: &Uri<String>) -> Result<Value, Box<dyn std::error::Error + Send + Sync>> {
        // Custom retrieval logic
        Ok(json!({}))
    }
}

let schema = json!({
    "$ref": "https://example.com/user.json"
});
let validator = jsonschema::async_options()
    .with_draft(Draft::Draft202012)
    .with_retriever(MyRetriever)
    .build(&schema)
    .await?;

I hope it should be enough for the majority of use cases