Merge branch 'bump-Django' into 'master'

.gitlab-ci.yml

Dockerfile

Dockerfile.binary

arkindex/dataimport/tests/test_imports.py

arkindex/dataimport/tests/test_process_elements.py

arkindex/documents/managers.py

arkindex/documents/tests/test_classes.py

arkindex/documents/tests/test_corpus_elements.py

arkindex/documents/tests/test_parents_elements.py

arkindex/images/apps.py

arkindex/project/settings.py

arkindex/sql_validation/indexer_prefetch_v2.sql

arkindex/users/tests/test_generic_memberships.py

arkindex/users/tests/test_providers.py

base/requirements.txt