Fix for redirect action path to take account of Discourse sub-directory base URL

[sindbach]

A patch for authorize path to take account of Discourse deployments with subdirectory base URL i.e. www.discourse.com/foo/bar.

Currently it will try to go to URL only on the top level domain i.e. www.discourse.com/authorize?supplier_id=1 where it should have included the subdirectories. i.e. www.discourse.com/foo/bar/authorize?supplier_id=1

[angusmcleod]

@sindbach Sure thing! Looks like we're getting a qunit failure on this. Do you want to have a go at addressing it? If not I'll take a look in the next few days.

[sindbach]

I'll try to take a look when I have the chance early next week.
I worked around this bug for our subscription authorisation, so no blocked on this .

Thanks Angus