Call BeforeAppendModel on embedded types

[jeffreydwalter]

Would be nice if BeforeAppendModel on embedded types was call so you could do something like the following:

type AuditFields struct {
    Created time.Time
    Updated *time.Time
}

var _ bun.BeforeAppendModelHook = (* AuditFields)(nil)

func (a * AuditFields) BeforeAppendModel(ctx context.Context, query bun.Query) error {
	if a == nil {
		a = new(AuditFields)
	}
	now := time.Now()
	switch query.(type) {
	case *bun.InsertQuery:
		a.Created = &now
	case *bun.UpdateQuery:
		a.Updated = &now
	}
	return nil
}

type User struct {
    AuditFields

    ID int64 ...
}

Here's a potential solution:

func (m *structTableModel) BeforeAppendModel(ctx context.Context, query Query) error {
    if !m.structInited {
        if err := m.initStruct(); err != nil {
            return err
        }
    }

    if m.table.HasBeforeAppendModelHook() {
        if err := m.invokeBeforeAppendModelHook(ctx, query, m.strct); err != nil {
            return err
        }
    }

    // Check and invoke hooks on embedded models
    return m.invokeEmbeddedBeforeAppendModelHooks(ctx, query, m.strct)
}

func (m *structTableModel) invokeBeforeAppendModelHook(ctx context.Context, query Query, value reflect.Value) error {
    if hook, ok := value.Addr().Interface().(schema.BeforeAppendModelHook); ok {
        return hook.BeforeAppendModel(ctx, query)
    }
    return nil
}

func (m *structTableModel) invokeEmbeddedBeforeAppendModelHooks(ctx context.Context, query Query, value reflect.Value) error {
    for i := 0; i < value.NumField(); i++ {
        field := value.Field(i)
        fieldType := field.Type()

        if fieldType.Kind() == reflect.Struct {
            if err := m.invokeEmbeddedBeforeAppendModelHooks(ctx, query, field); err != nil {
                return err
            }
        } else if fieldType.Kind() == reflect.Ptr && !field.IsNil() && field.Elem().Kind() == reflect.Struct {
            if err := m.invokeEmbeddedBeforeAppendModelHooks(ctx, query, field.Elem()); err != nil {
                return err
            }
        }

        // Check if the field itself implements the hook
        if field.CanAddr() {
            if err := m.invokeBeforeAppendModelHook(ctx, query, field); err != nil {
                return err
            }
        }
    }
    return nil
}