Function validate_input 

pub fn validate_input(
    value: &Value,
    field_path: &str,
    rules: &[ValidationRule],
) -> Result<()>

Validate JSON input against validation rules.

This function recursively validates a JSON value against a set of validation rules, collecting all errors that occur.

Errors

Returns FraiseQLError::Validation if any rule is violated (e.g., string too short, value out of range, or a required field is null).