User session

[darkdarkdragon]

What does this pull request do? Explain your changes. (required)
Join couple of transcoding sessions to
one 'user' session in recordings

Specific updates (required)

• add 'previousSessions' field to the AuthWebhook response
• in /recordings handler use 'previousSessions' field's content to find all the transcoding sessions belonging to this one
  'user' session and join them to one manifest

How did you test each of these updates (required)
Manually

Does this pull request close any open issues?

Checklist:

• README and other documentation updated
• Node runs in OSX and devenv
• All tests in ./test.sh pass

[yondonfu]

Would be nice to have a unit test for checking the session merging functionality.

[darkdarkdragon]

@yondonfu added unit test

[yondonfu]

Thanks for adding the unit test. Would also be nice to have that new behavior in the HandleRecordings handler to be unit tested, but the handler is pretty hefty and creating the necessary stubs may be tricky so if you feel like manual testing did the trick then I think that's ok.

LGTM