Feature request: Add redirectUrl query parameter support to `/service/logout` endpoint

[bobular]

For the delete account button work (VEuPathDB/web-monorepo#1493) it would be great if the /service/logout also took a redirectUrl query parameter (like login already does). Currently it seems not to, and always redirects to the homepage on success.

We will be redirecting to a /a/app/user/message/account-deleted route, to give a bit more feedback to the user.

I'll need to check that this page reliably works for guest users. Not sure at the moment (though this is not in the scope of this ticket!)

[bobular]

@ryanrdoherty has code for this already maybe