Replaced config SCHEME with Flask's own PREFERRED_URL_SCHEME setting.

This prevents us from explicitly passing SCHEME to url_for() calls.

NOTE: this possibly requires an update to your config_local.py

pillar/auth/oauth.py

@@ -74,8 +74,7 @@ class OAuthSignIn(metaclass=abc.ABCMeta):
         pass
 
     def get_callback_url(self):
-        return url_for('users.oauth_callback', provider=self.provider_name,
-                       _external=True, _scheme=current_app.config['SCHEME'])
+        return url_for('users.oauth_callback', provider=self.provider_name, _external=True)
 
     @staticmethod
     def auth_code_from_request() -> str: