PSR-15 middlewares are hooks on steroids for HTTP requests.
Due to chaining middlewares and the core request handler(s),
middlewares can execute code before and after the application.

Middlewares may return early, that means they can prevent
consecutive middleware and the core application from being executed
at all.

A full middleware coverage for *all* requests will need
a lot of changes to the core and extensions.
We'll eventually need to stop using header()/exit()/die()
or HttpUtility::{redirect,sendRespose}(). Those method calls
need to be replaced by manipulation of PSR-7 message objects.

PSR-15 interfaces are provided by psr/http-server-middleware:

composer require psr/http-server-middleware:^1.0

Change-Id: Ia906d51da2e4309a37fb47a7966b52f873782d8f
Releases: master
Resolves: #83725
Reviewed-on: https://review.typo3.org/55544


Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>