[FIX] Establish basic compatibility for TYPO3 v11

[krausandre]

I've done some basic stuff to make this extension usable with TYPO3 v11.5 and EXT:cart v.8.2.0.
(I had to add a version to composer.json, otherwise I could't use it.)

Testet with:

• PayPal sandbox
• PHP 7.4.
• TYPO3 11.5.6
• EXT:cart 8.2.0
• EXT:cart_products 4.0.3

[extcode]

Hi, I merged your code locally, because it has to be merged to the main branch.
I changed your first commit a little bit.

[krausandre]

Okay, that's cool. So we can close this pull request if you want?

[extcode]

I have to revert the changes in PaymentController because $this->htmlResponse()->withStatus() is not available in TYPO3 v10.

[krausandre]

So you suggest to turn off the deprecation log on each system, which uses the cart_paypal extension?
Well, this solution will work for now, but in v12 this will stuck in errors messages:
Deprecation: #92784 - Extbase controller actions must return ResponseInterface

[extcode]

Yes, the deprecation log should always be turned off in the live system. But in TYPO3 v11 $this->htmlResponse()->withStatus() should always be used, because $this->response is not set.

The next major version is compatible to TYPO3 v11 and v12. So the next version will always use the $this->htmlResponse()->withStatus() and will always return an ResponseInterface. I don't see a problem here, do you?

[krausandre]

OK I got it. I'm fine with it.