WIP - Unavailability Flow

[timarney]

@emanelfy here's the preview link for this feature https://ircc-development-pr-438.herokuapp.com/calendar

⭐️ You should be able to do a full run at this point explanation, review page and the updated email to the user.

What's missing?

• The NoJS flow we'll need direction (we can also discuss launching without that in place and than adding)
• We'll get the translations in once we're all set on this PR
• Will this go through a round of testing prior to going live? Or will we launch and tweak further as needed?