Switch from datalogic-rs v4 to v3

[Copilot]

Downgrades datalogic-rs dependency from version 4 to version 3 per project requirements.

Changes

• Cargo.toml: datalogic-rs = "4.0" → "3.0" (resolves to v3.1.1)

• Custom operator trait migration: All operators (FractionalOperator, StartsWithOperator, EndsWithOperator, SemVerOperator) migrated from v4's Operator trait to v3's CustomOperator trait with arena-based allocation

  • Method: add_operator() → register_custom_operator()
  • Signature: Returns &'a DataValue<'a> via arena instead of owned Value
  • Imports: ContextStack, Error, Evaluator → CustomOperator, DataArena, EvalContext, LogicError

• Evaluation calls: evaluate_json(str, str) → evaluate_str(str, str) due to v3 signature changes

API Example

Before (v4):

impl Operator for FractionalOperator {
    fn evaluate(&self, args: &[Value], context: &mut ContextStack, _: &dyn Evaluator) 
        -> Result<Value> {
        Ok(Value::String(result))
    }
}
logic.add_operator("fractional".to_string(), Box::new(FractionalOperator));

After (v3):

impl CustomOperator for FractionalOperator {
    fn evaluate<'a>(&self, args: &'a [DataValue<'a>], _: &EvalContext<'a>, arena: &'a DataArena) 
        -> Result<&'a DataValue<'a>> {
        let s = arena.alloc_str(&result);
        Ok(arena.alloc(DataValue::String(s)))
    }
}
logic.register_custom_operator("fractional", Box::new(FractionalOperator));

Behavior Change

Missing variables now return null per JSON Logic spec (v3 behavior) rather than throwing errors (v4 behavior). Updated test_eval_fractional_missing_var to reflect spec-compliant behavior.

Original prompt

I want to switch to datalogic-rs version 3 instead of 4. Open a pull request with the changes please

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