[services] Tunnelbroker - Tests for validateUUIDv4 function

Summary: This diff introduces tests for a validateUUIDv4 function from D4467 which validate generated UUIDs.

Test Plan: Expected test results on run yarn test-tunnelbroker-service-in-sandbox.

Reviewers: karol-bisztyga, palys-swm

Reviewed By: karol-bisztyga, palys-swm

Subscribers: ashoat, palys-swm, Adrian, atul, karol-bisztyga, yayabosh

Differential Revision: https://phab.comm.dev/D4468