CI: Add testrun for "psr/http-message" v2 with slim

[Chris53897]

in composer.json "psr/http-message" v1 and v2 are allowed.

But if i see this correct, v2 is never tested in the testruns.
Example:
https://github.com/php-http/message/actions/runs/7623563875/job/20763848547

Because of Version 3 of "slim/slim"
https://github.com/php-http/message/blob/1.x/composer.json#L31C10-L31C19

https://packagist.org/packages/slim/slim#3.12.5

Only the dev-version supports v1 and v2
https://packagist.org/packages/slim/slim#4.x-dev

[dbu]

hm, tricky :-/

maybe we should remove these optional integrations from require-dev and only require them for specific test runs. we could tag the tests about the integrations and only run tests with that tag in a build where we requite them. that would make the rest of the tests run with the latest and greatest for proper testing.

[Chris53897]

I just noticed that there is a testrun for php 8.2 where "slim/slim" is removed in ci.
https://github.com/Chris53897/message/actions/runs/7624004757/job/20765252556

But maybe with the latest dev-version of "slim/slim" this could be run on every php version.