[WIP] Log JSON API error messages

[pcraig3]

⚠ Update: this issue is related to the JSON stuff, yes, but it more properly lives under a "logging" epic which I haven't created yet. ⚠

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This issue is about what we do when we get an error message.

Ideally, we have all our validation logic & error message strings in models.py and they are being used by the API to return errors for bad inputs. That's all presumed by this issue.

This issue is about making sure that any errors users run into are also logged in our console, so that we can potentially find them later. There is another ticket about this (#90), so if we have settled on a format, we should follow it. If not, we should make sure messages are at least being spat out to the console.

All to say, our API routes should log errors when they see them, in addition to returning error messages to the user.