Resolve "Run full register printout generation in background"

Closes #229

See merge request !310

Revert "Merge branch 'fix/rename-late-tardiness' into 'master'"

See merge request !309

This reverts merge request !308

Rename last occurences of late to tardiness

See merge request !308

Resolve "Substitution teacher can't see any persons in the lesson view"

Closes #228

See merge request AlekSIS/official/AlekSIS-App-Alsijil!307

Drop support for GitHub

See merge request !306

Add distinct to group-based statistic views (extra marks and excuse types)

See merge request !305

Resolve "Use iconify for Material Icons instead of icon font"

Closes #213

See merge request !292

Release 2.1.1

See merge request !304

Resolve "Seating plan integration uses wrong permission names"

Closes #225

See merge request !302

Resolve "Students are listed multiple times in class register views"

Closes #219

See merge request !294

Switch to AlekSIS-Core==2.11

See merge request !303

Fix LessonDocumentationOnHolidaysDataCheck

Closes #223

See merge request !301

Resolve "Menu validator fails on register absence item"

Closes #224

See merge request !299

Co-authored-by: Jonathan Weth <git@jonathanweth.de>

Resolve "Print view fails sometimes with KeyError"

Closes #221

See merge request !296