Filter assignments by course

[JonasWanke]

Please merge #256 first!
Closes: #145

AssignmentsScreen can now be filtered by course. This also includes quick-filtering by tapping the course-chip on an AssignmentCard and parsing the query string from incoming deep links.

Known issues:

• I didn't get DraggableScrollableSheet to work inside a ModalBottomSheet, so there is an overflow if the SortFilter sheet is higher than the screen.

Screenshots

SortFilter sheet	Active course filter

[unicorn-bot]

⚠️ Unicorn Report

⚠️ 3 Warnings

• refactor(app): cleanup CategoryFilter update

  Co-Authored-By: Marcel Garus [email protected]

• Merge branch 'master' into issue/145-filter-assignments-by-course
• Merge branch 'master' into issue/145-filter-assignments-by-course

ℹ️ 1 Info

• This PR will close the following issues: Filter assignments by course #145

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[janrenz]

What if the list of courses gets too long?

[JonasWanke]

@janrenz The intended effect would be a scrollable sheet (probably using DraggableScrollableSheet), but I didn't get that to work yet (i.e., it currently overflows the screen). We will still merge this PR and look into scrolling soon (#260).