Adding support of unique_id

[lunarok]

Hi,

Trying to edit by GUI the properties of entities coming from ics, I get the message that it's missing the unique_id.
With some other integrations, it's possible to add it in configuration.yaml. But for ics, if I add it, HA is complaining that the conf file contains unvalid parameter at that line.
I search and see that there was some customize module with hidden parameter before, but it's not avalaible anymore. So to remove from the auto-generated dashboard or place it in other room for exemple, seems only solution now is to add the support of unique_id