correct service_whitelist dao/rest functionality

additionally added dao tests

tests/app/dao/test_service_whitelist_dao.py

@@ -0,0 +1,25 @@
+import uuid
+
+from app.models import ServiceWhitelist
+from app.dao.service_whitelist_dao import (#
+    dao_fetch_service_whitelist,
+    dao_add_and_commit_whitelisted_contacts,
+    dao_remove_service_whitelist
+)
+
+
+def test_fetch_service_whitelist_gets_whitelists(sample_service_whitelist):
+    whitelist = dao_fetch_service_whitelist(sample_service_whitelist.service_id)
+    assert len(whitelist) == 1
+    assert whitelist[0].id == sample_service_whitelist.id
+
+def test_fetch_service_whitelist_ignores_other_service(sample_service_whitelist):
+    assert len(dao_fetch_service_whitelist(uuid.uuid4())) == 0
+
+def test_add_and_commit_whitelisted_contacts_saves_data(sample_service):
+    whitelist = ServiceWhitelist.from_string(sample_service.id, 'foo@example.com')
+    dao_add_and_commit_whitelisted_contacts([whitelist])
+
+    db_contents = ServiceWhitelist.query.all()
+    assert len(db_contents) == 1
+    assert db_contents[0].id == whitelist.id