Allow client errors marked as "transient" to include link to status page

[jhiemstrawisc]

An interesting thought that goes back to a conversation we had long ago -- if the client encounters a transfer error it believes to be temporary and related to the overall federation (like a director outage), can we find a way to provide a link to a pre-configured status page that may provide information about the outage?

For example, maybe OSPool EPs are configured with some Pelican config so that if a transient error is encountered, the error/hold message has a link to https://status.osg-htc.org. This might help us cut down on the influx of user support tickets that show up any time we touch the Director.

We might also link to the Director itself, because can display origin issues for specific namespaces. If the client gets a 404 no origins found for path /foo/bar, maybe then can check the Director to see that the origin for /foo/bar is having issues.