Update vendor slack-go/slack (#1068)

vendor/github.com/slack-go/slack/block_conv.go

@@ -56,20 +56,16 @@ func (b *Blocks) UnmarshalJSON(data []byte) error {
 			block = &ContextBlock{}
 		case "divider":
 			block = &DividerBlock{}
+		case "file":
+			block = &FileBlock{}
 		case "image":
 			block = &ImageBlock{}
 		case "input":
 			block = &InputBlock{}
 		case "section":
 			block = &SectionBlock{}
-		case "rich_text":
-			// for now ignore the (complex) content of rich_text blocks until we can fully support it
-			continue
-		case "file":
-			// for now ignore the file blocks until we can fully support it
-			continue
 		default:
-			return errors.New("unsupported block type")
+			block = &UnknownBlock{}
 		}
 
 		err = json.Unmarshal(r, block)
@@ -253,12 +249,36 @@ func (a *Accessory) UnmarshalJSON(data []byte) error {
 			return err
 		}
 		a.DatePickerElement = element.(*DatePickerBlockElement)
-	case "static_select":
+	case "plain_text_input":
+		element, err := unmarshalBlockElement(r, &PlainTextInputBlockElement{})
+		if err != nil {
+			return err
+		}
+		a.PlainTextInputElement = element.(*PlainTextInputBlockElement)
+	case "radio_buttons":
+		element, err := unmarshalBlockElement(r, &RadioButtonsBlockElement{})
+		if err != nil {
+			return err
+		}
+		a.RadioButtonsElement = element.(*RadioButtonsBlockElement)
+	case "static_select", "external_select", "users_select", "conversations_select", "channels_select":
 		element, err := unmarshalBlockElement(r, &SelectBlockElement{})
 		if err != nil {
 			return err
 		}
 		a.SelectElement = element.(*SelectBlockElement)
+	case "multi_static_select", "multi_external_select", "multi_users_select", "multi_conversations_select", "multi_channels_select":
+		element, err := unmarshalBlockElement(r, &MultiSelectBlockElement{})
+		if err != nil {
+			return err
+		}
+		a.MultiSelectElement = element.(*MultiSelectBlockElement)
+	default:
+		element, err := unmarshalBlockElement(r, &UnknownBlockElement{})
+		if err != nil {
+			return err
+		}
+		a.UnknownElement = element.(*UnknownBlockElement)
 	}
 
 	return nil
@@ -285,9 +305,18 @@ func toBlockElement(element *Accessory) BlockElement {
 	if element.DatePickerElement != nil {
 		return element.DatePickerElement
 	}
+	if element.PlainTextInputElement != nil {
+		return element.PlainTextInputElement
+	}
+	if element.RadioButtonsElement != nil {
+		return element.RadioButtonsElement
+	}
 	if element.SelectElement != nil {
 		return element.SelectElement
 	}
+	if element.MultiSelectElement != nil {
+		return element.MultiSelectElement
+	}
 
 	return nil
 }