[MM-40638] Type all of the websocket event names as a new type WebsocketEventType (#25454)

Co-authored-by: Sudheer Tripathi <sudheer@clearglass.com>
Co-authored-by: Sudheer Tripathi <31629433+sudheer121@users.noreply.github.com>
Co-authored-by: Sudheer Tripathi <tripathisudheer604@gmail.com>

server/channels/app/post_acknowledgements.go

@@ -126,7 +126,7 @@ func (a *App) GetAcknowledgementsForPostList(postList *model.PostList) (map[stri
 	return acknowledgementsMap, nil
 }
 
-func (a *App) sendAcknowledgementEvent(event string, acknowledgement *model.PostAcknowledgement, post *model.Post) {
+func (a *App) sendAcknowledgementEvent(event model.WebsocketEventType, acknowledgement *model.PostAcknowledgement, post *model.Post) {
 	// send out that a acknowledgement has been added/removed
 	message := model.NewWebSocketEvent(event, "", post.ChannelId, "", nil, "")