Use plugins and condition to create advanced policies

This request is very similar to ✨ Allow multiple purge cron jobs Active

@vbouchet are you still interested in this feature?

Work in progress:

Feedback welcome!

All conditions have been implemented:

Policies can inherit from the global configuration settings:

And the policy configuration is now translatable.

Anyone interested in a 5.x-dev release?

A new condition has been added that allows to postpone deletion until the user has been properly notified.

Automatically closed - issue fixed for 2 weeks with no activity.