Generalized "GitHub Webhook + Contributor Role -> Rewards" Contributor Class v2

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Extending on #46 we should be able to identify the user's "class"

In the next iteration, we should identify the user's "class"

1. specification author - the original author of the task
2. assignee - they are the one responsible for the deliverable
3. collaborator - they are added to the org/repo as an official team member
4. contributor - the default option