Add support for Guzzle 7

The mailgun/mailgun-php library uses php-http/discovery to automatically discover and use PSR18 client implementations. Guzzle 7 implements PSR18 while Guzzle 6 does not. This means that applications require no further dependencies if they use Guzzle 7 as discovery should find Guzzle 7 automatically. While applications that need Guzzle 6 require the php-http/guzzle6-adapter so that Guzzle 6 is discovered automatically.

No code changes or other work should be required.

The suggestion for which I created an MR is to make the php-http/guzzle6-adapter as a suggestion instead of dependency. This way, it is up to the developer to decide whether they need to require it or not. They will then have 3 options.

• If they are on Guzzle 7 already, nothing to do.
• If they are on Guzzle 6, require php-http/guzzle6-adapter at the application's root composer.json file.
• If they are on Guzzle 6, require some other PSR18 http client implementation.

This should be documented in the release notes, and the module's documentation.

I like the suggestion. Since we don't have direct Guzzle usage, it doesn't make sense to keep it in the requirements.
I created a new version - 2.0.x with DEV release only. It's ready for testing on Drupal 10 installations.

I'll keep the issue open because I also want to do some testing on real projects.
Thanks!

Mailgun 2.0.0 is out: https://www.drupal.org/project/mailgun/releases/2.0.0 →
Thanks!

On Drupal 9.5.10 I'm getting a fatal error on the status page:

No PSR-18 clients found. Make sure to install a package providing "psr/http-client-implementation". Example: "php-http/guzzle7-adapter"

I'm on PHP 8.1, php-http/guzzle7-adapter requires PHP ^7.2.

Most likely, you have guzzle ^6.x.

You have to add manually php-http/guzzle6-adapter: composer require php-http/guzzle6-adapter
Just tested using Drupal 9.5.10 and PHP 8.1.

Automatically closed - issue fixed for 2 weeks with no activity.