define isort first party (app and tests)

we were seeing isort produce different outputs locally and in docker -
this was due to it having different opinions about whether the tests
module (ie all our unit tests) is a first party (local) or third party
(pip installed) import. It's a first party import, so by defining this
in the setup.cfg isort settings, we can force it to be consistent
between environments.

Note: I don't know why it was different in the first place though

tests/app/main/views/test_verify.py

@@ -4,6 +4,7 @@ import uuid
 from bs4 import BeautifulSoup
 from flask import url_for
 from itsdangerous import SignatureExpired
+
 from tests.conftest import normalize_spaces