Show dial-in number for running meetings

[SamuelWei]

Is your feature request related to a problem? Please describe.
Once a room is running, PILOS can get the phone number and the PIN from the API.
This should be shown in the frontend as an alternative to joining with the web browser.

Describe the solution you'd like

• Capture dial-in number and pin during create call
• Save in the database
• If number is not one of the invalid numbers, show in the frontend: link to click on and qr code to scan

[SamuelWei]

Design idea

[rasos]

Ideally we also show the numbers for any meeting room, so that the number can be communicated in advance, before the meeting started.

This could be achieved with an additional table in the frontend. However, when load balancing, we would need some mechanism to assign the call to the BBB node which handles the meeting. To make the number predictable, this would require an additional FreeSwitch and a simple API call. I have sketched here how that could work: https://git.fairkom.net/hosting/fairteaching/-/issues/147#note_80907