[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/plugin_api.go

@@ -957,7 +957,7 @@ func (api *PluginAPI) KVList(page, perPage int) ([]string, *model.AppError) {
 }
 
 func (api *PluginAPI) PublishWebSocketEvent(event string, payload map[string]any, broadcast *model.WebsocketBroadcast) {
-	ev := model.NewWebSocketEvent(fmt.Sprintf("custom_%v_%v", api.id, event), "", "", "", nil, "")
+	ev := model.NewWebSocketEvent(model.WebsocketEventType(fmt.Sprintf("custom_%v_%v", api.id, event)), "", "", "", nil, "")
 	ev = ev.SetBroadcast(broadcast).SetData(payload)
 	api.app.Publish(ev)
 }