district: Refactor and update

district/migrations/0002_auto_20210205_1514.py

district/models.py

district/templates/district/base.html

district/templates/district/district_article_page.html

district/templates/district/district_articles_page.html

district/templates/district/district_contact_page.html

district/templates/district/district_people_page.html

district/templates/district/district_person_page.html

district/templates/district/district_tags_page.html

shared/models.py

shared/templates/shared/article_preview.html