Move error handling to middleware

[emostov]

EDIT: Removed the sanitize numbers middleware. No monkey patching express functions for now.

Closes #138

This PR is a combination of two related features that both affect the implementation of get and post. This is in preparation for merging #134 as that PR does not use a generic wrapper around express app.get and app.post.'

Motivation

Middleware functions are modular, can be put on routes/routers with fine grain control, and are individually tested-able.

• With our current setup of error handling we must have duplicate code across get and post.

• The handling of different errors is intertwined and number sanitization is all done in one function, making good unit testing difficult.

• When adding new types of error formats or phasing out old error formats there is a high cognitive over head with the current setup. Using middleware specific to an error formats will allow us to easily add or remove error formats from our codebase

• For number sanitization, having the functionality at the middleware level allows us to move it from the application level to the router level if we choose. The current layout I propose is at the application level as that mimics our current API

What to look for while reviewing

• Make sure there are no hanging responses. Express does not natively catch errors thrown by async functions, so it is up to the try/catch wrappers in get and post to catch them.
• All error responses are the same as before. I tried to ensure that we handle all error formats the same way, but good to double check
• The modification of res.send is reasonable. Implementing this was tricking because
  1. I needed to ensure the correct binding of res to the original send and
  2. I had to do some generic typing that got a bit finicky since some of the types from @types/express had several any defaults and sanitizeNumbers is all anys