Error handling that does not suck.

[mykeels]

This PR introduces error handling that adheres to the following rules:

• Errors in the controller are handled via a mapping of error names to http status codes. All unmapped errors default to an InternalServerError.
• Errors in the service are handled via a mapping of error names to higher-level, human-readable errors.
• When working with async methods that throw errors, we want to use await to ensure that try-catch works.