Function run_program 

pub fn run_program(
    user_key: &mut String,
    world: &mut Tree<String, Vessel>,
    program: Vec<Action>,
) -> Result<ActionResult, Box<dyn Error>>

Runs the provided program on the provided world-state, possibly modifying the provided user key.

• user_key: The key of the user’s active Vessel.
• world: The mutable world-state.
• program: The set of Actions to be run.

Returns an ActionResult informing the client of what to tell the user, if successful.

Errors:

This method fails if any of the Actions fails.