Re-create backend test suite in Jest

[h1divp]

With recent updates to the formulas used to gather the correct distances from a user to a stored message or geolocation, we need to make sure that this is properly tested. This will also be useful for any future updates to our algorithms used for distance checking and nearby message retrieval. Make sure to use Jest for this, but if you have a better framework or proposal then please message a tech lead.

1. Test coordinates that should be within the bounds of a message retrieval radius, to see if the message is actually received by a client.
2. Test coordinates outside of this radius to make sure that these messages are not received.

Playing with obscure coordinates, large and small distances with different radii, etc are all welcome. We want to test this as thoroughly as possible.

Research Jest testing, especially for websockets as a starting point.

[aaditkamat]

Can I work on this?