Here are the key steps to create the class handler and BAPI wrapper in the SAP backend:
1. Create a class handler (e.g. ZXX_CREATE_FLIGHT_BOOKING) by copying from a template class
(e.g. Z00_CREATE_FLIGHT_BOOKING)
2. Generate and activate the class
3. Create a BAPI wrapper function module (e.g. ZXX_BAPI_CRT_FLIGHT_BOOKING) by copying from
a template function module (e.g. Z00_BAPI_CRT_FLIGHT_BOOKING)
4. Assign the function module to a function group