HTTP error pages
Right now HTTP error codes just throw errors in the console. We should have nice helpful error pages.
Helpful error pages do things like:
- Explain the problem in plain language
- Offer a link or buttom to get back to a working state of the app
- Allow technical detail to be provided if that's secure/useful
- If the problem is actionable, explain what, if anything, the user can do about the problem, or explain that it's being dealt with some other way