Fix a bunch more DeprecationWarning

[simonw]

================================================================================================== warnings summary ===================================================================================================
tests/test_asgi_csrf.py: 35 warnings
  /Users/simon/Dropbox/Development/asgi-csrf/.venv/lib/python3.10/site-packages/httpx/_client.py:1437: DeprecationWarning: The 'app' shortcut is now deprecated. Use the explicit style 'transport=ASGITransport(app=...)' instead.
    warnings.warn(message, DeprecationWarning)

tests/test_asgi_csrf.py: 27 warnings
  /Users/simon/Dropbox/Development/asgi-csrf/.venv/lib/python3.10/site-packages/httpx/_client.py:1570: DeprecationWarning: Setting per-request cookies=<...> is being deprecated, because the expected behaviour on cookie persistence is ambiguous. Set cookies directly on the client instance instead.
    warnings.warn(message, DeprecationWarning)

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html
=========================================================================================== 48 passed, 62 warnings in 0.17s ===========================================================================================

[simonw]

I'm using this to find them:

pytest -W error -x

[simonw]

Got them all passing, need to fix this:

/Users/simon/Dropbox/Development/asgi-csrf/.venv/lib/python3.10/site-packages/pytest_asyncio/plugin.py:208: PytestDeprecationWarning: The configuration option "asyncio_default_fixture_loop_scope" is unset.
The event loop scope for asynchronous fixtures will default to the fixture caching scope. Future versions of pytest-asyncio will default the loop scope for asynchronous fixtures to function scope. Set the default fixture loop scope explicitly in order to avoid unexpected behavior in the future. Valid fixture loop scopes are: "function", "class", "module", "package", "session"

  warnings.warn(PytestDeprecationWarning(_DEFAULT_FIXTURE_LOOP_SCOPE_UNSET))