Choose most specific domains first

If we had organisations for GDS and Cabinet Office, then we’d always
want someone whose email address ends in `@cabinet-office.gov.uk` to
match to `cabinet-office.gov.uk` before matching to
`digital.cabinet-office.gov.uk`.

Sorting the list by shortest first addresses this.

app/dao/organisation_dao.py

@@ -1,3 +1,5 @@
+from sqlalchemy.sql.expression import func
+
 from app import db
 from app.dao.dao_utils import transactional
 from app.models import (
@@ -28,7 +30,8 @@ def dao_get_organisation_by_email_address(email_address):
 
     email_address = email_address.lower()
 
-    for domain in Domain().query.all():
+    for domain in Domain.query.order_by(func.char_length(Domain.domain).desc()).all():
+
         if (
             email_address.endswith("@{}".format(domain.domain)) or
             email_address.endswith(".{}".format(domain.domain))

tests/app/service/test_rest.py

@@ -271,6 +271,10 @@ def test_create_service_with_domain_sets_organisation(
     expected_org,
 ):
 
+    red_herring_org = create_organisation(name='Sub example')
+    create_domain('specific.example.gov.uk', red_herring_org.id)
+    create_domain('aaaaaaaa.example.gov.uk', red_herring_org.id)
+
     org = create_organisation()
     create_domain('example.gov.uk', org.id)
     create_domain('test.gov.uk', org.id)