Fixed updating username in settings view

The timestamps used by the 'last viewed' property of the video progress
feature were converted to strings when sending to the frontend, but never
changed back to timestamps when PUTting via the SDK. I solved it by not
PUTing the user at all, but using PATCH to set the username instead.

tests/test_web/test_user_settings.py

@@ -0,0 +1,37 @@
+import flask
+import flask_login
+from pillar.tests import AbstractPillarTest
+
+
+class UsernameTest(AbstractPillarTest):
+    def setUp(self, **kwargs) -> None:
+        super().setUp(**kwargs)
+        self.user_id = self.create_user()
+
+    def test_update_via_web(self) -> None:
+        from pillar.auth import current_user
+        import pillar.web.settings.routes
+
+        with self.app.app_context():
+            url = flask.url_for('settings.profile')
+
+        with self.app.test_request_context(
+                path=url,
+                data={'username': 'je.moeder'},
+                method='POST',
+        ):
+            self.login_api_as(self.user_id)
+            flask_login.login_user(current_user)
+            pillar.web.settings.routes.profile()
+
+        db_user = self.fetch_user_from_db(self.user_id)
+        self.assertEqual('je.moeder', db_user['username'])
+
+    def test_update_via_patch(self) -> None:
+        self.create_valid_auth_token(self.user_id, 'user-token')
+        self.patch(f'/api/users/{self.user_id}',
+                   json={'op': 'set-username', 'username': 'je.moeder'},
+                   auth_token='user-token')
+
+        db_user = self.fetch_user_from_db(self.user_id)
+        self.assertEqual('je.moeder', db_user['username'])