Additional optional config fields

[mdugas]

Is your feature request related to a problem? Please describe.
There is currently no way to define a set event start/end date for a VPN config to have a valid set time window, ensuring that as the event nears completion the latest config cannot be valid past the end of the event.

Describe the solution you'd like

1. The ability to define the start, end date and config availability date of an event. The system should refuse to generate the config if the current time is before the config availability timestamp or after the event end date. During the event, it should generate a config that is valid until the end date of the event, up to a maximum of the vault configured max TTL.

Describe alternatives you've considered
N/A - Feature design to be completed

Additional context
N/A