fix: ensure driver.Valuer.Value() is called for simple arguments

The convertSimpleArgument function now properly handles driver.Valuer interface
by calling the Value() method when the argument implements driver.Valuer.
This ensures that custom value types implementing driver.Valuer are correctly
processed before being passed to the PostgreSQL type encoding system.

This change makes the behavior consistent between simple and extended query
protocols regarding driver.Valuer handling.

Author: cruvie

values.go

@@ -1,6 +1,7 @@
 package pgx
 
 import (
+	"database/sql/driver"
 	"errors"
 	"reflect"
 	"time"
@@ -16,6 +17,15 @@ const (
 )
 
 func convertSimpleArgument(m *pgtype.Map, arg any) (any, error) {
+	// If arg implements driver.Valuer, use Value method
+	if valuer, ok := arg.(driver.Valuer); ok && valuer != nil {
+		v, err := valuer.Value()
+		if err != nil {
+			return nil, err
+		}
+		arg = v
+	}
+
 	fieldValue := reflect.ValueOf(arg)
 	switch fieldValue.Kind() {
 	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64: