[MM-58492][MM-58523] Fixed some access control bugs around archived channels by replacing the permission check with HasPermissionToReadChannel (#27409)

* [MM-58492][MM-58523] Fixed some access control bugs around archived channels by replacing the permission check with HasPermissionToReadChannel

* Fix lint, add ChannelId to uploads

* Fix MMCTL tests and remove unnecessary check for the error message that doesn't work anyways

* Include channel map for getting flagged posts

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

server/channels/app/upload.go

@@ -271,6 +271,7 @@ func (a *App) UploadData(c request.CTX, us *model.UploadSession, rd io.Reader) (
 	}
 
 	info.CreatorId = us.UserId
+	info.ChannelId = us.ChannelId
 	info.Path = us.Path
 	info.RemoteId = model.NewString(us.RemoteId)
 	if us.ReqFileId != "" {