Generic state machine framework.
- A callback that is triggered when the state activates.
- A callback that is triggered when the state deactivates.
- A transition that is triggered one time by a future.
- The state machine itself.
- A transition that triggers a nested state machine.
- State of the state machine.
- A transition that is triggered through a stream.
- A transition that happens automatically after a certain duration elapsed.
- A transition from one state to another.