Use one SQL query to get all domains

[quis]

Domains must have an organisation ID, so are always associated with an organisation:

notifications-api/app/models.py

Line 380 in aee7023

organisation_id = db.Column("organisation_id", UUID(as_uuid=True), db.ForeignKey("organisation.id"), nullable=False)

The previous query gets all the domains for all organisations, no matter whether they are archived, have no services, etc.

This does the same thing but in one SQL query, rather than firing off one query per organisation.

Tested here:

notifications-api/tests/app/dao/test_organisation_dao.py

Lines 61 to 73 in aee7023

	def test_dao_get_organisation_domains(notify_db_session):
	create_organisation("org_1", domains=["dept_of_health.com", "eg.com"])
	create_organisation("org_2", domains=["other.com", "number10.com"])
	create_organisation("org_3", domains=["my_org.gov", "whitechapel.com"])
	assert set(dao_get_organisation_domains()) == {
	"dept_of_health.com",
	"eg.com",
	"other.com",
	"number10.com",
	"my_org.gov",
	"whitechapel.com",
	}