Resolve "Improve the formatting of the substitution plan"

Closes #152

See merge request !206

Merge local master to new empty branch

Resolve "Substitution is shown on regular/print timetable"

Closes #149

See merge request !205

Provide fixtures for testing/demo instances

See merge request !204

Update poetry.lock

See merge request !203

Update changelog from 2.0rc3

See merge request !202

(cherry picked from commit e07e0794)

Translations update from Weblate

See merge request !186

Currently translated at 100.0% (127 of 127 strings)

Translation: AlekSIS/AlekSIS-App-Chronos
Translate-URL: https://translate.edugit.org/projects/aleksis/aleksis-app-chronos/de/

Currently translated at 100.0% (127 of 127 strings)

Translation: AlekSIS/AlekSIS-App-Chronos
Translate-URL: https://translate.edugit.org/projects/aleksis/aleksis-app-chronos/de/

Currently translated at 7.0% (9 of 127 strings)

Translation: AlekSIS/AlekSIS-App-Chronos
Translate-URL: https://translate.edugit.org/projects/aleksis/aleksis-app-chronos/fr/

Update translation files

See merge request AlekSIS/official/AlekSIS-App-Chronos!200

Support also dates for TimePeriod's methods get_datetime_start/_end

See merge request !197

Resolve "Force __str__ methods to return strings"

Closes #151

See merge request !198

Update poetry.lock

See merge request !199

Update changelog from 2.0rc2

See merge request !195

(cherry picked from commit 869379e7)

Remove merge leftovers in changelog

See merge request !193

Drop usage of non-existing permission in permission rules for lesson substitutions

See merge request !192

Update poetry.lock

See merge request !190

Update the changelog from 2.0rc1

See merge request !189

(cherry picked from commit e039025b)

Resolve "Use correct semantic html elements"

Closes #146

See merge request !184

Resolve "Fix range check in next_lesson"

Closes #147

See merge request !185