finish requirements for admin, implement private information in frontend, permissions

contracts/admin.py

contracts/migrations/0004_alter_contract_options_and_more.py

contracts/models.py

contracts/templates/contracts/view_contract.html

contracts/views.py

registry/admin.py

registry/templates/admin/index.html

shared/templatetags/__init__.py

shared/templatetags/markdownify.py

users/models.py