Basic testing using flask-testing

This commit makes it possible to override settings during tests, by
switching capsulflask/__init__.py to a "create_app" pattern, and using
`dotenv_values` instead of `load_dotenv`.

The create_app() method returns a Flask app instance, to give
more control over when to initialise the app. This allows setting
environment variables in test files.

Then, use dotenv_values to override loaded .env variables with ones from
the environment, so that tests can set `POSTGRES_CONNECTION_PARAMETERS`
and `SPOKE_MODEL` (possibly others in future..).

Inital tests for the "landing" pages, and login / activation, are
included.

capsulflask/tests/test_auth.py

@@ -0,0 +1,23 @@
+from flask import url_for, session
+
+from capsulflask.db import get_model
+from capsulflask.tests_base import BaseTestCase
+
+
+class LoginTests(BaseTestCase):
+    render_templates = False
+
+    def test_login_request(self):
+        with self.client as client:
+            response = client.get(url_for("auth.login"))
+            self.assert_200(response)
+
+            # FIXME test generated login link
+
+    def test_login_magiclink(self):
+        token, ignoreCaseMatches = get_model().login('test@example.com')
+
+        with self.client as client:
+            response = client.get(url_for("auth.magiclink", token=token))
+            self.assertRedirects(response, url_for("console.index"))
+            self.assertEqual(session['account'], 'test@example.com')

capsulflask/tests/test_landing.py

@@ -0,0 +1,14 @@
+from capsulflask.tests_base import BaseTestCase
+
+
+class LandingTests(BaseTestCase):
+    #: Do not render templates, we're only testing logic here.
+    render_templates = False
+
+    def test_landing(self):
+        pages = ['/', 'pricing', 'faq', 'about-ssh', 'changelog', 'support']
+
+        with self.client as client:
+            for page in pages:
+                response = client.get(page)
+                self.assert_200(response)