Allow announcements to be expired with a button

[KevinMulhern]

Because:

• When I want an announcement to expire early, I want to be able to do that by clicking a button in the announcement instead of changing the expiry date.

Notes:

• We'll need to add a status enum to announcements with active and expired values
• A scheduled job to run every day that will set the status of announcements that have an expiry date in the past to "expired"