Add yarn dependency "select2-materialize" in settings.py so that select2-materialize statics can be accessed from everywhere

Resolve "Synchronise AlekSIS groups with Django groups"

Closes #221

See merge request AlekSIS!214

Resolve "Add age_at method and age property"

Closes #220

See merge request AlekSIS!212

Resolve "Add a description field to Person"

Closes #218

See merge request AlekSIS!211

Resolve "Add support for defining group types"

Closes #217

See merge request AlekSIS!213

[Docker] Add celery as an extra to Dockerfile

See merge request AlekSIS!210

Fix celery config

See merge request AlekSIS!209

[Docker] Introduce multistage build

See merge request AlekSIS!208

Update forms

See merge request AlekSIS!206

- Add ExtensibleForm
- Allow strings for layout nodes
- Add layouts

Introduce text collapsible

See merge request AlekSIS!205

Resolve "Mich-Seite"

Closes #207

See merge request AlekSIS!203

Resolve "Many fields too short"

Closes #206

See merge request AlekSIS!202