Added unhandledRejection error handling to koa app

[deanhannigan]

Description

Uncaught promise rejections in the Google Sheets integration would eventually be caught in the uncaughtException handler in the koa app. This would then terminate the server.

This fix adds general handling for uncaught rejections in the koa app and logs any events to bb-alert

Addresses

• Add await when processing header to avoid unhandleRejection #698 node-google-spreadsheet#2

Launchcontrol

Add handling for uncaughtRejection in the koa app.

[mike12345567]

Hey @deanhannigan - we actually intentionally don't handle stuff like this, as an unhandled promise like is coming from the googlesheets library is a severe issue we want the process to crash and make us aware something very bad has happened.

We had build protections in place for our backend services to avoid unhandled promises via static analysis but for libraries we don't have this luxury - however when it does happen its best we're made aware as directly as possible.