Maven dependency proxy: shorten workhorse send+upload timeout

🔥 Problem

The maven dependency proxy heavily relies on the following features of workhorse:

• Gitlab::Workhorse.send_url.
• Gitlab::Workhorse.send_dependency.

Both features will use a similar logic: get a file from a url.

The problem is: that url could be pointing to an address that will never answer. We thus hit a request timeout in those occasions.

That timeout:

• is quite long, 30 seconds from our observations.
• will log and return a 500 error.

🚒 Solution

• Add support for an option to use a reduced timeout, like 10 seconds.
• Not sure if there is a better error than the 500. What would be good to describe that the url is an not valid one. 400 Bad Request?