Use upstream slack-go/slack again (#1018)

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

@@ -0,0 +1,30 @@
+package slack
+
+// InputBlock defines data that is used to collect information from users -
+// it can hold a plain-text input element, a select menu element,
+// a multi-select menu element, or a datepicker.
+//
+// More Information: https://api.slack.com/reference/messaging/blocks#input
+type InputBlock struct {
+	Type     MessageBlockType `json:"type"`
+	BlockID  string           `json:"block_id,omitempty"`
+	Label    *TextBlockObject `json:"label"`
+	Element  BlockElement     `json:"element"`
+	Hint     *TextBlockObject `json:"hint,omitempty"`
+	Optional bool             `json:"optional,omitempty"`
+}
+
+// BlockType returns the type of the block
+func (s InputBlock) BlockType() MessageBlockType {
+	return s.Type
+}
+
+// NewInputBlock returns a new instance of an Input Block
+func NewInputBlock(blockID string, label *TextBlockObject, element BlockElement) *InputBlock {
+	return &InputBlock{
+		Type:    MBTInput,
+		BlockID: blockID,
+		Label:   label,
+		Element: element,
+	}
+}