Fix instance returned by MessageResponseTrait

[AJenbo]

The PSR-7 ResponseInterface states that the method here should return an instance of the same class as the method is being called on but the trait instead returned an instance of the underlying implementation. Simply returning $this resolves the issue and likely is also what is intended by the ResponseInterface having a return type of static.

Note that the failing tests here are the same as on the main branch and not related to the changes

[ezimuel]

This PR from a PHPStan point of view is right but it doesn't work properly since the various withProtocolVersion(), withHeader(), etc do not return values. Thanks anyway for the contribution, you helped me to solve most of the PHPStan issues in #1442

[ezimuel]

We need to return the withProtocolVersion($version) otherwise we'll lost the response. We cannot return $this, the PSR-7 MessageInterface is immutable.

[AJenbo]

In that case you need to do a bigger refactoring in order to resolve this properly. withProtocolVersion() should not return a different implementation of MessageInterface. Maybe it would be better to make a function for getting the response object, not no longer implement MessageInterface in the wrapper.

[AJenbo]

maybe a good solution would be to clone the object and swap the response object with the new one and then return that.

[ezimuel]

I think this is more a PHPStan issue rather that a real PHP one. In the meantime we'll leave the extra comment to prevent the error message from PHPStan.

[AJenbo]

It's not PHPStan specific, since it's the PHPDoc it's obviously not PHP specific either since the whole point of PHPDoc is to express type information that isn't possible in PHP.

See the original debate from when they added it to the interface: zendframework/zend-diactoros#37 (comment) / php-fig/fig-standards#793 (comment)

The intended meaning is clearly to return an instance of the same class as the one the method was invoked on, not simply any class that implements the interface.