feat(bun): generate native Go array slices for PostgreSQL array columns

Bun's pgdialect scans/appends native slices directly, so array columns
(text[], integer[], uuid[], ...) always generate as plain []string,
[]int32, etc. with an explicit "array" bun tag, regardless of --types
(sqltypes/stdlib/baselib). The SqlXxxArray wrapper types are no longer
used for Bun array columns (gorm is unaffected and keeps using them).

Adds --array-nullable pointer_slice to represent nullable array columns
as *[]T instead of []T, so callers can distinguish SQL NULL (nil) from
'{}' (pointer to an empty slice). Verified end-to-end against a live
PostgreSQL instance for NULL/{}/populated arrays in every --types mode.

Closes #13

vendor/github.com/uptrace/bun/dialect/pgdialect/append.go

@@ -0,0 +1,87 @@
+package pgdialect
+
+import (
+	"database/sql/driver"
+	"fmt"
+	"reflect"
+	"time"
+
+	"github.com/uptrace/bun/dialect"
+	"github.com/uptrace/bun/schema"
+)
+
+var (
+	driverValuerType = reflect.TypeFor[driver.Valuer]()
+
+	stringType      = reflect.TypeFor[string]()
+	sliceStringType = reflect.TypeFor[[]string]()
+
+	intType      = reflect.TypeFor[int]()
+	sliceIntType = reflect.TypeFor[[]int]()
+
+	int64Type      = reflect.TypeFor[int64]()
+	sliceInt64Type = reflect.TypeFor[[]int64]()
+
+	float64Type      = reflect.TypeFor[float64]()
+	sliceFloat64Type = reflect.TypeFor[[]float64]()
+
+	timeType      = reflect.TypeFor[time.Time]()
+	sliceTimeType = reflect.TypeFor[[]time.Time]()
+)
+
+func appendTime(buf []byte, tm time.Time) []byte {
+	return tm.UTC().AppendFormat(buf, "2006-01-02 15:04:05.999999-07:00")
+}
+
+var mapStringStringType = reflect.TypeOf(map[string]string(nil))
+
+func (d *Dialect) hstoreAppender(typ reflect.Type) schema.AppenderFunc {
+	kind := typ.Kind()
+
+	switch kind {
+	case reflect.Ptr:
+		if fn := d.hstoreAppender(typ.Elem()); fn != nil {
+			return schema.PtrAppender(fn)
+		}
+	case reflect.Map:
+		// ok:
+	default:
+		return nil
+	}
+
+	if typ.Key() == stringType && typ.Elem() == stringType {
+		return appendMapStringStringValue
+	}
+
+	return func(gen schema.QueryGen, b []byte, v reflect.Value) []byte {
+		err := fmt.Errorf("bun: Hstore(unsupported %s)", v.Type())
+		return dialect.AppendError(b, err)
+	}
+}
+
+func appendMapStringString(b []byte, m map[string]string) []byte {
+	if m == nil {
+		return dialect.AppendNull(b)
+	}
+
+	b = append(b, '\'')
+
+	for key, value := range m {
+		b = appendStringElem(b, key)
+		b = append(b, '=', '>')
+		b = appendStringElem(b, value)
+		b = append(b, ',')
+	}
+	if len(m) > 0 {
+		b = b[:len(b)-1] // Strip trailing comma.
+	}
+
+	b = append(b, '\'')
+
+	return b
+}
+
+func appendMapStringStringValue(gen schema.QueryGen, b []byte, v reflect.Value) []byte {
+	m := v.Convert(mapStringStringType).Interface().(map[string]string)
+	return appendMapStringString(b, m)
+}