Ref: OM17-3 / DECOM-19

Is your feature request related to a problem? Please describe.

As a visitor, I don't want to join a videoconference before or after has happened.

Describe the solution you'd like

I want that the videoconference option is accessible only when the meeting is about to happen (30 minutes before) or when it's on course, but not after has happened.

Describe alternatives you've considered

To have a configuration with an input like:

"Number of minutes before this external iframe will be visible"

But this is probably a symptom of the Yet Another Setting Syndrome that we suffer in Decidim.

There is a gist with a hack for having this. See specially the shouldMeetingBeVisible function.

Additional context

This comes from the "EPIC: Control visibility and access to online meetings" (#7724)

Acceptance criteria

• Given that there's a meeting configured with iframes
  and I visit this page 10 minutes before the meeting will start
  then I must see the external iframe.
• Given that there's a meeting configured with iframes
  and I visit this page 40 minutes before the meeting will start
  then I must not see the external iframe.
• Given that there's a meeting configured with iframes
  and I visit this page 10 minutes after the meeting has started
  then I must see the external iframe.
• Given that there's a meeting configured with iframes
  and I visit this page 10 minutes after the meeting has ended
  then I must not see the external iframe.