api: Expose LastSyncError on ExternalService
Created by: ryanslade
Add a new LastSyncError
field on the ExternalService
node in our API
This returns the optional sync error that exists on the most recent sync for an external service.
Note that currently errors caused by bad credentials will NOT show up since we don't treat that as an error and instead simply remove all repos for the external service. Another PR will handle this special case.