When working with background events locally, it can be difficult to construct the payload correctly. If you are missing the data or context properties, the framework will raise an HTTP 400 response without actionable details. (#83 addresses documentation)

## Current Behavior

The current framework response is:

```

400 Bad Request

Bad Request

The browser (or proxy) sent a request that this server could not understand.

The current log output is:
```
127.0.0.1 - - [16/Apr/2021 12:38:05] "POST / HTTP/1.1" 400 -
```

## Expected behavior

Log output should specify payload validation errors down to the property & type level.