Allow group administrator to invite people to its group via invitation link

[psrok1]

Feature Category

• Correctness
• User Interface / User Experience
• Performance
• Other (please explain)

Describe the problem

We can choose group admin within MWDB groups, but currently the only superpower given to them is removing people from groups.

Describe the solution you'd like

MWDB should provide a way to invite people to the common group as well.

We should be concerned that default sharing rule is All my groups, so invitation requires explicit consent of both parties to join the common group. Proposed workflow:

• Group admin generates invitation link via https://mwdb.cert.pl/profile/group/<group-name> providing name of user they want to invite
• Group admin sends link to the chosen user
• User goes into the link and is asked whether they want to join group XYZ
• If they click 'Yes', user joins the group and https://mwdb.cert.pl/profile/group/<group-name> is presented.

Link should have limited expiration time (e.g. 1 week). It would be best to make it one-time and be inactivated after joining group, but that might be a little bit harder to implement.