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

Closes #228

See merge request !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

Merge branch '220-register-absence-isn-t-usable-without-direct-access-to-class-register' into 'master'

Resolve "Register absence isn't usable without direct access to class register"

Closes #220

See merge request !295

Translations update from Weblate

See merge request !289

Currently translated at 100.0% (289 of 289 strings)

Translation: AlekSIS/AlekSIS-App-Alsijil
Translate-URL: https://translate.edugit.org/projects/aleksis/aleksis-app-alsijil/uk/

Currently translated at 100.0% (289 of 289 strings)

Translation: AlekSIS/AlekSIS-App-Alsijil
Translate-URL: https://translate.edugit.org/projects/aleksis/aleksis-app-alsijil/ru/

Release 2.1

See merge request !290