* [feat] Added program_uuids to notify_credentials mgmt cmd

[MICROBA-951]

To support updating a users credentials in the Credentials services for
all users enrolled in a program we have added a command line argument to
the notify_credentials command called program_uuids. This supports a
list of program uuids. It will retrieve all course runs in the listed
programs and update the related credentials data.

* updated comments