Defguard enrollment should not enforce phone number

[syphernl]

Is there a reason the enrollment process in the client expects the user to enter their phone number?

I understand why it would need an email but what is the reasoning behind requiring a phone number? Luckily 00000 is accepted so that can be used as a workaround for people who prefer not to enter their phone number.

[teon]

Duplicate of https://github.com/DefGuard/proxy/issues/52