Training content should be stored in the database

[ragesoss]

We've been gradually stretching the TrainingModule, TrainingLibrary, and TrainingSlide classes beyond their original design, and the storage strategy is breaking down for the on-wiki training modules on P&E Dashboard.

We currently import training module content from the wiki, and we cache the entire collection of TrainingLibrary.all, TrainingModule.all, and TrainingSlide.all in respective Rails cache keys. This means that updating the content is more complex and interdependent than it ought to be, and we're running up against the (default) limits of our cache infrastructure as well. (By default memcached has a 1M limit on file size, and P&E Dashboard now requires more than that. For now, I've increased the max memcached file size on the server.)

We should instead be storing all the training content in ActiveRecord, I think. We could then easily update individual slides and modules without worrying as much about the interdependence. A slide belongs to a module, and a module belongs to a library. Easy peasy.

This will involve:

• Turning the training classes into ActiveRecord models (and maybe turn TrainingBase into a module).
• Updating TrainingLoader to work with those models and their relations.

[ragesoss]

@bcb37 FYI, in case you haven't seen it, this is related to the work you've been doing.

[bcb37]

Yeah, I have come up against the memcached limit. This makes a lot of sense. I could take it on next.

[ragesoss]

This has been done for TrainingSlide. TrainingModule and TrainingLibrary ought to be converted to ActiveRecord at some point, but for now they aren't causing any real problems.

[ragesoss]

This is done for TrainingModule, so only TrainingLibrary is left.

[ragesoss]

Done, thanks to @AmitJoki