GREG-85: Parsing mobile phone if it is coming from server. Adding a test

Adding and fixing some logic relating to showing phone numbers. Now the number is parsed correctly if it is sent from the server.

frontend/src/routes/guest/register/index.test.tsx

@@ -36,7 +36,6 @@ beforeEach(() => {
   )
 })
 
-// This is just an example of how jest-fetch-mock can be used, it is not a proper test
 test('Mobile phone number parsed and split correctly', async () => {
   render(
     <LocalizationProvider dateAdapter={AdapterDateFns}>