// Package valid wraps github.com/go-playground/validator/v10 behind a minimal
// Validator interface, returning xerrors-typed errors with stable codes.
//
// The backend library is fully hidden — callers interact only with Validator
// and *xerrors.Err. Swapping the backend in the future requires no API changes.
//
// Usage:
//
//	v := valid.New()
//	if err := v.Struct(req); err != nil {
//	    // err is *xerrors.Err with Code() == xerrors.ErrInvalidInput
//	    // err.Fields()["field"] contains the failing field name
//	}
//
//	// Spanish messages
//	v := valid.New(valid.WithMessageProvider(valid.SpanishMessages))
//
// Struct tags follow go-playground/validator conventions:
//
//	type CreateUserReq struct {
//	    Email string `json:"email" validate:"required,email"`
//	    Age   int    `json:"age"   validate:"min=18"`
//	}
package valid