facet-validate 0.42.0

Validation attributes for facet - validate field values during deserialization
Documentation 
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# facet-validate

Field validation during deserialization for the facet ecosystem.

## Features

- Validation runs **during deserialization**, so errors include source spans (e.g., pointing to the exact JSON location)
- Custom validators with meaningful error messages via `Result<(), String>`
- Auto-deref: `fn(&str)` validators work for `String` fields

## Usage

```rust
use facet::Facet;
use facet_validate as validate;

fn validate_positive(n: &i64) -> Result<(), String> {
    if *n <= 0 {
        Err(format!("must be positive, got {}", n))
    } else {
        Ok(())
    }
}

#[derive(Facet)]
struct Product {
    #[facet(validate::custom = validate_positive)]
    price: i64,
}
```

## Built-in Validators

| Validator | Syntax | Applies To |
|-----------|--------|------------|
| `min` | `validate::min = 0` | numbers |
| `max` | `validate::max = 100` | numbers |
| `min_length` | `validate::min_length = 1` | String, Vec, slices |
| `max_length` | `validate::max_length = 100` | String, Vec, slices |
| `email` | `validate::email` | String |
| `url` | `validate::url` | String |
| `regex` | `validate::regex = r"..."` | String |
| `contains` | `validate::contains = "foo"` | String |
| `custom` | `validate::custom = fn_name` | any |

## Integration

Enable the `validate` feature on `facet-json` (or other format crates):

```toml
[dependencies]
facet-json = { version = "0.41", features = ["validate"] }
facet-validate = "0.41"
```