OCPP201: Add trigger_reason argument

[Pietfried]

Describe your changes

Added trigger_reason to on_transaction_finished since libocpp API is updated. Moved conversion from stop_reason to trigger_reason from libocpp to OCPP201 module

Issue ticket number and link

Companion PR in libocpp: https://github.com/EVerest/libocpp/pull/698

Checklist before requesting a review

• [x] I have performed a self-review of my code
• [ ] I have made corresponding changes to the documentation
• [x] I read the contribution documentation and made sure that my changes meet its requirements