Switch to official PSR-15 psr/* packages

[mindplay-dk]

Switching to the official PSR-15 packages psr/http-server-middleware and psr/http-server-handler, sadly, is a breaking change.

You will need to live with the deprecation notice for the foreseeable future, likely for a couple of years, because a breaking change to this package means incompatibility with the current, existing body of available middleware.

Worse, the breaking change in middleman will propagate to breaking changes in every project and library that depends on it, which in my case means cascading breaking changes to around four dozen packages, again, with cascading breaking changes to every project depending on those.

There is simply no way I can justify spending this amount of time on a meaningless circus of dependency juggling again, since the container PSR also recently force everyone to go this route.

If you find this frustrating as all hell, you can go and thank the maintainers who refuse to listen when I argue that a proposed PSR should start with the Psr namespace - so that, come approval, all we need to do is switch to a new package that replaces the unofficial package.

This entire fucking circus could be avoided so easily with a little planning ahead.

Meanwhile, you can enjoy your deprecation notices for the next 2-3 years, until there's an actual reason for a major release of this package.

Yeah, FUCK.