Allow trailing slash in the PROXY_ENDPOINT.

[coltfred]

We discovered that if you put a trailing slash in the PROXY_ENDPOINT then you'll end up with the TSP dumping ERRO Rejection(NotFound).

This is confusing to the consumer. We should just detect that the trailing slash is present and strip it when they create the client.

Also, we should log the URL that was attempted to be hit when we log a 404 so it's more obvious to see what URL was hit and why it wasn't successful.

[BobWall23]

When done with this, create a ticket in the node TSC to do the work there as well.