Disable user_loading on arbitrary endpoints

[lukasjuhrich]

To be dealt with after #370.

For some reason, loading an asset while being logged in (i.e., being handled by the static endpoint) triggers the user loader, causing a lot of API calls – but there should be None, we don't need any information about the user when serving, say, a .css file.

There should be a (regression) test for this, as this has a significant performance impact.

[lukasjuhrich]

A comparison: https://agdsn.de/sipa/news…
logged in:

logged out:

[lukasjuhrich]

What triggers the user loader on /static endpoints is the use of current_user in the log method:

Traceback (most recent call last):
  File "/home/lukas/.virtualenvs/sipa/lib/python3.10/site-packages/flask/app.py", line 2095, in __call__
    return self.wsgi_app(environ, start_response)
  File "/home/lukas/.virtualenvs/sipa/lib/python3.10/site-packages/werkzeug/middleware/proxy_fix.py", line 187, in __call__
    return self.app(environ, start_response)
  File "/home/lukas/.virtualenvs/sipa/lib/python3.10/site-packages/flask/app.py", line 2080, in wsgi_app
    response = self.handle_exception(e)
  File "/home/lukas/.virtualenvs/sipa/lib/python3.10/site-packages/flask/app.py", line 2077, in wsgi_app
    response = self.full_dispatch_request()
  File "/home/lukas/.virtualenvs/sipa/lib/python3.10/site-packages/flask/app.py", line 1525, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/home/lukas/.virtualenvs/sipa/lib/python3.10/site-packages/flask/app.py", line 1521, in full_dispatch_request
    rv = self.preprocess_request()
  File "/home/lukas/.virtualenvs/sipa/lib/python3.10/site-packages/flask/app.py", line 1861, in preprocess_request
    rv = self.ensure_sync(before_func)()
  File "/home/lukas/code/10ag/sipa/sipa/blueprints/generic.py", line 34, in log_request
    extra={'tags': {'user': get_user_name(current_user),
  File "/home/lukas/code/10ag/sipa/sipa/utils/__init__.py", line 112, in get_user_name
    if user.is_authenticated:
  File "/home/lukas/.virtualenvs/sipa/lib/python3.10/site-packages/werkzeug/local.py", line 436, in __get__
    obj = instance._get_current_object()
  File "/home/lukas/.virtualenvs/sipa/lib/python3.10/site-packages/werkzeug/local.py", line 565, in _get_current_object
    return self.__local()  # type: ignore
  File "/home/lukas/.virtualenvs/sipa/lib/python3.10/site-packages/flask_login/utils.py", line 26, in <lambda>
    current_user = LocalProxy(lambda: _get_user())
  File "/home/lukas/.virtualenvs/sipa/lib/python3.10/site-packages/flask_login/utils.py", line 384, in _get_user
    current_app.login_manager._load_user()
  File "/home/lukas/.virtualenvs/sipa/lib/python3.10/site-packages/flask_login/login_manager.py", line 355, in _load_user
    user = self._user_callback(user_id)
  File "/home/lukas/code/10ag/sipa/sipa/base.py", line 38, in load_user
    raise RuntimeError
RuntimeError

(I artificially injected the RuntimeError to get a stacktrace)