Online Meetings with videconferences

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

As an administrator on the last couple weeks I'm receiving lots of requests to have online meetings.

Describe the solution you'd like

I would want to have an option when configuring a Meeting where I can select if the Meeting is Online or Presential.

If it's Presential (default selection on admin panel) then it should work as usual (with Location/Map).

If it's Online then:

* It should allow me to add an URL for the videoconference or streaming service that's going to be used

* It should not allow to add a Location nor try to find this location through the Geocoder

* It should have an URL field validation

* It should not appear on the Meetings map

We should also add a "Method" filter on Meetings so they're discoverable someway. It should have two options:

* Online: all the legacy meetings (already created before this new issue)

* Presential: we should hide the map for these kind of meetings

https://i.imgur.com/79GjRVt.png

https://i.imgur.com/Z1WgbHU.png

For better discoverability, we must also change the "map-marker" icon on the card, it should have a "external-link" icon:

https://i.imgur.com/G3f1UvK.png

On the future it'd nice to also have an embed feature for these kind of contents (like embedding youtube streammings or jitsi videoconferences). This could be extended to other videoconfence services.

Describe alternatives you've considered

At the moment the workaround that we found is:

* Add Location as "Barcelona" (as in "all the city")

* Add Location Hint with the URL of the videoconf/streaming service

Additional context

This is related with the isolation / COVID19 situation.

Does this issue could impact on users private data?

No

Acceptance criteria

- [ ] As an administrator I can add a Presential Meeting (as usual)

- [ ] As an administrator I can add an Online Meeting

- [ ] As an administrator I can only add URLs to this field

- [ ] As a visitor I have a filter to navigate Meetings by "method"