fix save_with_state_error

[mathieu-valery]

Hi Ched,

The purpose of this PR is to fix save_with_state since it returns true when a transition is invalid
In my use case if an operator tries to transition payment procedure from canceled to to_process), it silently fails since no @registered_callbacks gets registered then no transition is operated which I think is misleading the operator.

we can add an error if the transition is not possible but further fixes are needed :

1. need to define private reader method def #{field_name} because it is needed by active record full_messages method
2. Important. : this line if #{virtual_attribute_name}_changed? didnt work as expected. It always return true because Rails sees this as a change from nil → 'canceled', even though the effective value is the same. We need {virtual_attribute_name}.to_s != #{field_name}_current_state.to_s to check that state didnt change. In Sidecare some forms submit the current_state_value (payment procedure for instance) and without this proper check, these forms will always fail to update the instances

Hope you like it

[chaadow]

Thanks a lot! I'll cut a release

[chaadow]

@mathieu-valery Released in v0.2.7