Add enrolment token expiration to system sesstings

[kchudy]

• Ability for the admin to set the enrolment token expiration using the UI
• Informing enrolled users in the notification when will the token expire

[teon]

@j-chmielewski did you add this already to settings?

[teon]

@j-chmielewski close or add this to settings task.

[j-chmielewski]

Done with #2132