Merge branch 'mkdocs_material' into 'master'

.gitlab-ci.yml

Dockerfile

docker-compose.yml

docs/accessibility/accessibility.md

docs/architecture/admin-gui.md

docs/architecture/admin-tools.md

docs/architecture/api-gateway.md

docs/architecture/cms.md

docs/architecture/monitoring.md

docs/architecture/services/authentication.md

docs/architecture/services/csv-catalog-downloader.md

docs/architecture/services/elasticsearch/elasticsearch.md

docs/architecture/services/elasticsearch/indexer.md

docs/architecture/services/legacy-auth-middleware.md

docs/architecture/services/mail.md

docs/architecture/services/media-library.md

docs/architecture/services/organizations.md

docs/architecture/services/resources.md

docs/architecture/web-app.md

docs/assets/authentication-service.png