Add Role filter to group overview
## Problem There is currently no easy way to find projects where a user has a certain role in a group. ## Proposal Add a filter element to filter by role to the search bar, so that users can also search by: * `Role = Guest` * `Role = Reporter` * `Role = Developer` * `Role = Maintainer` * `Role = Owner` ![image](/uploads/5e119a6baede6a2fd49f70fb3033b023/image.png)
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