[MM-62427] Add message attachments validation (#30180)

* Add message attachments validation

* Add props validation

* Validate slack attachment fields

* Update tests and library usage

* Improve interactive dialog error for length checks

* Allow predefined colors for slack attachments

* Fix TestPostAction

* Use const for data source

* Add tests

* Cleanup unused props

* Add happy path tests

* lint fixes

* Add validation for PostActionOptions

server/public/pluginapi/experimental/panel/settings/bool_setting.go

@@ -75,6 +75,7 @@ func (s *boolSetting) GetSlackAttachments(userID, settingHandler string, disable
 		currentValueMessage = fmt.Sprintf("Current value: %s", currentTextValue)
 
 		actionTrue := model.PostAction{
+			Type: model.PostActionTypeButton,
 			Name: "Yes",
 			Integration: &model.PostActionIntegration{
 				URL: settingHandler,
@@ -86,6 +87,7 @@ func (s *boolSetting) GetSlackAttachments(userID, settingHandler string, disable
 		}
 
 		actionFalse := model.PostAction{
+			Type: model.PostActionTypeButton,
 			Name: "No",
 			Integration: &model.PostActionIntegration{
 				URL: settingHandler,