Bug fixes

Stable realease.
Minor bugfix.

Resolves issues with optimistic locking and prevents the triggering of handlers when a post is performed.

Fix notice from php 7.4

• D9 compatibility
• Refactoring of redundent code parts by introducing base classes and traits for the gateway plugins
• couple of minor fixes and tweaks found along the way
• code cleanup and several CS fixes
• Send a lot more data on (pre)authorization requests, such as cart item data, shipping address, etc
• Allow to choose the hash method
• Activate secure invoice - a separate issue for this will be opened though, as this is untested currently, also still missing some parameters in the actual capture request