refactor(bookings): use BookingsController from has_account_engine
refactor(bookings): use BookingsController from has_account_engine

The `has_accounts_engine` contains a full features BookingsController,
functionally identical to ours.

This patch drops the BookingsController.

xuewenfei/bookyt,hauledev/bookyt,huerlisi/bookyt,hauledev/bookyt,xuewenfei/bookyt,hauledev/bookyt,wtag/bookyt,xuewenfei/bookyt,huerlisi/bookyt,wtag/bookyt,huerlisi/bookyt,hauledev/bookyt,wtag/bookyt