[FEAT] Beta tester email whitelist

[NethminCodes]

Create a new UUID for every student we include in the beta-test, (which may include upto a 100 users, allowing them to each have a unique beta key so that a common one which can be spread around isn’t used.

[Joecey]

After discussing Nethmin, easiest way to do this is to create a whitelist table of all beta test users emails - then do a check against the table at login/sign up