[IMP] sale,purchase: allow invoicing

(closes #500)

(cherry picked from commit 84c0595aef3a417702c81b5226ae1f61817a2bf8)
[IMP]Added auto_confirmation field, seted default is true,override create method of event and event registration, to confirm event and subscription if auto_confirmation field is true.

[IMP]seted default value for auto_confirmation in ir_values and get values when create event and registration.

[IMP]Maked if condition one liner in registration create method.

[IMP]Improved yml test case for event, changed some value.

[REM]Removed constraint for create draft subscription when nb_register reached seat_max and for create draft subscription added one common method called from create and subscribe_to_event.

[IMP]Improved constraint message for availabel seat and improved some if condition to confirm registration.

[IMP]Improved if condition for confirm subscription

[IMP]Improved if condition seted and instead of or.

[IMP]Improved some code in create method of registration to confirm event.

[IMP]Added warning mesage when confirm registration manually and there are no availabel seat.

[IMP]Improved yml test cases.

[IMP]Improved typo mistake

[REV]Revert code for constraint and revert yml test case.

[IMP]Improved create method of subscription

[IMP]checked if event is confirm then confirm its subscription and improved yml test case.

[IMP]renamed method name.

[IMP]Impoved warning message for no availabel seat and added pop alert in website event when there are no availabel seat.

[IMP]Improved demo data for event

[REV]Revert code for add alert in website event sale.

[REM]Remove js for alert for event