API call: add an array of cases to a test run

[kj-brown]

Is your feature request related to a problem? Please describe.
Currently, our automated service creates a test run, finds all of the filtered test cases, and has to do a forEach to add all the relevant cases to a run. This s long and prone to errors.

Describe the solution you'd like
The ability to add an array of cases to a test run i.e. a TestRun.add_cases where the ids field would be an array of case IDs.