[Enhancement] Cost/booking linking

[edster]

Currently there is no way to link an existing cost to a booking/transport. When using MCP or manual entry, sometimes the cost gets created before the transport/booking it logged.

I would like to be able to have an option to select an existing cost, instead of only being able to create a new one.

[wivaku]

Related: Currently I can create a new cost for a booking (or transport), but not link a cost to an existing booking (or transport).

Another reason to combine the concepts of "booking" and "transport" (#2073)

And also: a single booking / transport might have multiple expenses.
E.g. for the flights there was the original cost, plus a cost later for a last minute upgrade.
Currently I can only add a single cost to a booking / transport.

[wivaku]

And also: I may want to unlink a cost. The option I have now in the Transports / Booking window: delete.

[mauriceboe]

coming in our next big release :)