PHP8 compatibility

[yoanmLf]

Hello,

May I propose a PR to allow PHP8 to be used on this project ?

I quickly checked, it looks like the lonely issue is php-http/client-common which is not compatible with PHP8.
I guess updating requirement from ^1.0 to ^1.0|^2.0 should be enough
Unfortunately without any tests some issue may appears at some points as some methods don't exist anymore on PHP8 :| I should be able anyway to double check that by using the branch on my project and check on my own CI if it's OK (at least for the part used by my project)

Based on changelog, It seems nothing need to be updated as removed options don't seems to be used there.

[yoanmLf]

FYI, did the update on my fork and executed PHPCS with php8 compatibility checker to ensure nothing will be broken.
It looks OK

Also checked for php 8.1, same result 👌

Let me know, If I can open a PR from there https://github.com/yoanmLf/php-rabbitmq-management-api.
ℹ️ Finally moved under TheFork, PHP 8 compatible version is available there https://github.com/lafourchette/php-rabbitmq-management-api/releases/tag/2.2.0
Thanks

[yoanmLf]

Another update is required for php-http/httplug, requirement should be ^1.0|^2.0 too. It seems there is no breaking change from v1 to v2 (as said This version is no BC break for consumers using HTTPlug. However, HTTP clients that implement HTTPlug need to adjust because we add return type declarations.)

[yoanmLf]

Just saw that PR #11 which looks like more or less the same as what I did