Test carddav connector

Taken from the most recent wiki status update:

The meeting prior, it was determined that the main goal over the next week(s) would be to build a simple, non-secure connection between a CardDAV server and Ensemble. This task would include a function that initiated such a connection, as well as a unit test to accompany it. Specifically, this would be done using the Radicale local CardDAV server software. This task was accomplished by developing a connection function that produced an OPTIONS HTTP Request towards a parametered server URL, which would return a positive result if the request status was successful (200). However, the function is not fully completed, as it seems to not address a failed connection response in the expected manner (i.e. A case in which it should not return a resolved promise, does). The recent push request needs to be looked over to see if any solutions can be found for these unexpected results, before the next steps can be taken.