Fix use with keyword arguments for Ruby 3.0

[walro]

The added test case would, prior to the fix, fail under Ruby 3.0, with the following error:

MiddlewareTest#test_handles_keyword_arguments_0:
ArgumentError: wrong number of arguments (given 2, expected 1)

The change itself was inspired by rack/rack#1505

[walro]

The failure on Ruby-head seems unrelated to the changes here.

[jkowens]

@zzak it looks like we have a couple issues with the CI. For some reason native extensions are failing on ruby-head, and we're missing a secret for SLACK_WEBHOOK_URL. I'm not familiar with Github Actions, does it have an "allowed failure" setting? That would be useful for ruby-head which is probably unstable.

[walro]

and we're missing a secret for SLACK_WEBHOOK_URL

I think that's because of "PRs from forks" are not allowed to access secrets (consider someone doing something like echo $SLACK_WEBHOOK_URL)

I'm not familiar with Github Actions, does it have an "allowed failure" setting?

To my understanding, nothing like Travis CI's allow_failure exists, but continue on error gets you pretty close.

I will submit a PR later today.

[walro]

I will submit a PR later today.

See #1703

Edit: That PR did not solve "fails on ruby-head", but it at least disables fail-fast which is a bit of an improvement.

[jkowens]

Thanks for your contributions!