Implement API endpoint for retrieving FQDNs of monitored dashboard devices

gso/api/v1/subscriptions.py

gso/products/__init__.py

gso/services/subscriptions.py

gso/workflows/tasks/import_iptrunk.py

gso/workflows/tasks/import_office_router.py

gso/workflows/tasks/import_router.py

gso/workflows/tasks/import_site.py

gso/workflows/tasks/import_super_pop_switch.py

test/api/conftest.py

test/api/test_subscriptions.py

test/fixtures.py

test/workflows/iptrunk/test_create_iptrunk.py

test/workflows/router/test_create_router.py

test/workflows/site/test_create_site.py