Implement chained badges

[gitsteph]

Hi! I'm not sure what the status was on this feature; seemed like it was partially implemented then commented out for some reason... submitting this since there weren't updates in the issue on it yet. :)

A few things I noticed/questions:

• It seems like new BadgeDefinitions will only create new Badges for all current GamificationInterfaces. If a new GamificationInterface is created and saved afterward, that won't receive the Badge with prior BadgeDefinitions.
• Along the same vein, if we were to later place a Badge (linked to a prior BadgeDefinition) on a new interface, e.g. by manually creating -> new_badge = Badge(badge_definition=instance_of_badge_def), that new_badge won't have fields such as name, description, etc. that would be populated by BadgeDefinition filled. Is the intent that a Badge would only ever be created via BadgeDefinition?
• Lastly, your example of awarding a badge points out that you'd grab all the badges then grab the first; that seems like that would always grab the same one though, right? (Rather than the first one that is not yet acquired)

Finally, thanks for maintaining this!!

(Related to Issue #3 )

[mattjegan]

Thanks for making the PR into the project, I'm always looking for help. Some great points you've mentioned above 😄 You're first point (interfaces not creating missing badges) is definitely a bug which we'll need to address at some point. As for the second point, I did originally intend for BadgeDefinitions to be used to create Badge instances automatically, do you think this could be improved or perhaps just documented better? Lastly, my example of using Badge.objects.first() was intended to demonstrate the use of Badge.award() rather than fetching of a particular Badge, perhaps this could also be documented better?

[mattjegan]

Thanks, looks correct to me 👍 I'll merge it in right now. One thing that I would perhaps recommend in the future is to split your tests into multiple smaller tests. In test_save, whenever you think you need another test_msg# that would indicate that you may need another test_ method instead 😄 Anyway, thanks for the awesome contribution and I hope that you may continue to contribute to this project.