Test Web Services with Blacklight

[pgwillia]

Is your feature request related to a problem? Please describe.
Over the Christmas break we will have a long Symphony outage due to re-indexing the database (which as crazy as it sounds takes close to 7 days). I [@kgood] want to try out the feasibility of pointing production UAL blacklight against Test web services for this outage window. My account and holds would still be unavailable but holdings info and ebook links would show up reducing the impact of this outage.

Describe the solution you'd like
I think making the Symphony Web Services target configurable would work well. Would be able to make changes like this in the future independent of code changes.

Describe alternatives you've considered
Changing the hard coded value https://github.com/ualbertalib/discovery/blob/master/app/services/symphony_service.rb#L55

Additional context
It may be cleanest to change the link within blacklight. If we point prod web services against the test Symphony we may be in a situation where various apps that us it beyond Blacklight (and that includes the entire Macewan web site) will be writing to the test DB which would be bad. I will dig deeper into this and get back.

Is https://github.com/ualbertalib/NEOSDiscovery/blob/master/app/services/symphony_service.rb#L61 also impacted?