Expiration date on partner pages

One-sentence description

Can you add a functionality to set an expiration date on profile pages of partners.

Motivation

Because it is pretty annoying to have to memorise the duration of all contracts. It would be way easier to just be able to set an expiration date when the contract enters.

Desired functionality

An extra date field in the admin page when editing/creating a partner page. When this date has passed, the profile page should automatically be set to inactive (maybe send a mail to extern@ to let the extern know when this happens).

Suggested implementation