[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/post.go

@@ -2087,7 +2087,7 @@ func (a *App) GetPostIfAuthorized(c request.CTX, postID string, session *model.S
 		return nil, err
 	}
 
-	if !a.SessionHasPermissionToChannel(c, *session, channel.Id, model.PermissionReadChannelContent) {
+	if !a.SessionHasPermissionToReadChannel(c, *session, channel) {
 		if channel.Type == model.ChannelTypeOpen && !*a.Config().ComplianceSettings.Enable {
 			if !a.SessionHasPermissionToTeam(*session, channel.TeamId, model.PermissionReadPublicChannel) {
 				return nil, model.MakePermissionError(session, []*model.Permission{model.PermissionReadPublicChannel})