Filter by assigned user should show groups the user is part of

[strassan]

When a card is only assigned to a group but not to a user it will never show up using the "Filter by assigned user" feature.

Steps to reproduce

1. Create a card and assign it to a group that's part of the board
2. Use "Filter by assigned user" and choose a user that is part of the very group

Current behavior

The card that was assigned to the group (and thus also to the user) does not show up.

Desired behavior

The card that was assigned to the group should show up.

Alternative

Alternatively the "Filter by assigned user" feature could also list the groups. Then you could choose the user and the corresponding group to the see all cards relevant to that user.