Merge branch 'release-3.0' into '840-urls-in-invitation-email-contains-the-django-prefix'

# Conflicts:
#   CHANGELOG.rst

CHANGELOG.rst

@@ -44,6 +44,7 @@ Fixed
 * Dynamic routes were not removed/hid when the respective object registering it was deleted.
 * Django messages were not displayed in Vue frontend.
 * Links to data check objects did not work properly.
+* Backend cleanup task for Celery wasn't working.
 * Urls in invitation email were broken.
 * Invitation view didn't work.
 * Invitation emails were using wrong styling. 

pyproject.toml

@@ -81,7 +81,7 @@ html2text = "^2020.0.0"
 django-ckeditor = "^6.0.0"
 calendarweek = "^0.5.0"
 Celery = {version="^5.2", extras=["django", "redis"]}
-django-celery-results = "^2.0.1"
+django-celery-results = "^2.5.1"
 django-celery-beat = "^2.2.0"
 django-celery-email = "^3.0.0"
 django-jsonstore = "^0.5.0"