district: Newsletter subscription form on home and conctacts page

...rations/0118_alter_districtcustompage_content_and_more.py

.../0119_districthomepage_newsletter_description_and_more.py

...igrations/0120_alter_districthomepage_content_and_more.py

district/models.py

district/templates/district/district_contact_page.html

district/templates/district/district_home_page.html

shared/blocks.py

...emplates/shared/blocks/newsletter_subscription_block.html

...rations/0047_alter_uniwebflexiblepage_content_and_more.py