Add support for Guzzle 7

[squatto]

Laravel 8 was released on 9/8/2020, and it increased Guzzle's minimum version requirement from ^6.3 to ^7.0.1. This unfortunately means that this package can't be used because it's requiring ~6.0.

One potential problem is that Guzzle 7 requires PHP >=7.2, so it would make a pretty big bump from your current >=5.5.0 requirement. Nobody should be using PHP 5.* at this point anyway. PHP 7.2 hasn't been actively supported since 11/30/2019, and PHP 7.3 only has active support until 12/6/2020, 2 months from now. Anybody that runs into issues with the version bump is likely having many more issues than just this package ;)

Looking through your package's source, I don't see anything in the Guzzle 6 to 7 upgrade guide that will cause any incompatibilities or problems. I don't think you'll need to change any code at all, actually. I haven't spun up a dev store to run the tests against yet though so I'm not 100% sure. I'd be happy to do that, if you'd like.

Thanks!

[Max84]

There is a pull request for that #34 since a few months. Maybe some admin can merge it?
Or @donutdan4114 needs some help to maintain this repo. Maybe @squatto or me can help ;)

[ew-andrew-sus]

Here is a pull request #37 for Guzzle ^7.2.0 version. Would be great to have a new release. It blocks already update Drupal Shopify module to 10 version.