Add Signal Group info, when team member has been approved

[blackthornedk]

Is your feature request related to a problem? Please describe.
There is no list of the team signal groups. After joining a team, it is not obvious if and how to join the relevant signal group.

Describe the solution you'd like
We should add info about the signal group, on the team page, visible for members.
We could also ass a join link for the group.

The Signal Volunteer Group Link could also be added.
Both links can be added to the email, that is sent, when a member joins a team.

[Easyjuhl]

The Signal Volunteer Group does not allow joining via Group Link yet.