Merge branch 'develop'

app/apps/api/serializers.py

app/apps/api/urls.py

app/apps/api/views.py

app/apps/core/models.py

app/apps/users/urls.py

app/apps/users/views.py

app/escriptorium/templates/core/document_form.html

app/escriptorium/templates/export/alto.xml

app/escriptorium/templates/export/pagexml.xml

app/escriptorium/templates/users/profile.html

app/escriptorium/templates/users/profile_api_key.html

app/escriptorium/templates/users/profile_files.html

app/escriptorium/templates/users/profile_group_list.html

app/escriptorium/templates/users/profile_invitations.html

app/requirements.txt

docker-compose.override.yml_example

docker-compose.yml

front/src/document_form.js

front/src/editor/store/document.js

front/vue/components/SegPanel.vue