Provide groups and username to context of the new ondemand.d config yamls

[ericfranz]

https://github.com/OSC/ondemand/pull/893 adds a new directory for yaml config files and it would be useful to have the rendering of the ERB here provide access to the groups and users

an eventual refactoring of something like this into something more general may be related to https://github.com/OSC/ondemand/issues/759

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[ericfranz]

The idea here is the context would minimally provide something like

username # => "efranz"
groups #=> ["PZS0714", "PZS0002", "PZS0530", "abaqus", "hpcsoft"... "PAS1788"]

Though having access to the OodSupport object or knowing the id and the name of a group a user is part of might both be useful.