Christian Kuhn authored Jun 23, 2021 and Benni Mack committed Jun 30, 2021

The patch changes the extbase Mvc/Request to implement
PSR-7 ServerRequestInterface: The former extbase request
details like 'controllerAction' are changed to an
PSR-7 attribute and the Request class is now a
decorator - it receives the original PSR-7 request
as constructor argument, then implements both the
extbase RequestInterface plus PSR-7 ServerRequestInterface.

This way, the Request object itself does not hold
state (except the original request), but channels
all get* and with* calls to the PSR-7 request object.
This avoids creating a new standalone object and moving
all data from the PSR-7 object into the new object.

The patch is relatively conservative. The extbase
related set* methods are kept even though they're
all @internal and violate immutability, and various
method signatures are not adapted towards strict
typing, yet. The reason for that are various
chain- and loop dependencies especially in fluid view
that should be solved with...