state_machine: Test whether an object can take a transition

When using state_machine Show archive.org snapshot you sometimes need to know whether an object may execute a certain transition. Let's take an arbitrary object such as a blog article as an example that has those states:

A -> B -> C -> D

Additionally, you have transitions between the states as shown above. Let's call the transition between 'A' and 'B' transition_ab for simplicity. \
Given an object in state 'A'. You can call object.transition_ab but calling object.transition_bc! will obviously fail because there's no such transition for state 'A'.

Now if you need to check whether you can call transition_ab or not, you can use object.can_transition_ab? which checks if an appropriate transition exists. \
This is often useful in views where might think about writing [state_A, state_B].include? object.state (which you should not).

Keep in mind that this will not call any validations or other filters on your object. The transition might still fail.