Change interface of functions to accept steps' parameters

[bkielbasa]

I'm thinking about changing the step's API a bit. Right now it's very simple.

type Func func(ctx context.Context) error

Parameters from steps are fetched using methods like below:

ctx.GetIntParam(0) -> returns the first parameter
ctx.GetIntParam(1) -> returns the second parameter

It works and was super easy to implement but operating on indexes isn't that user-friendly as it should be. I don't want to do much magic but there's an option to extend the interface to be more dynamic.
Using reflection, it's possible to dynamically pass those parameters to the function on the fly so users won't have to play with indexes.

func myCoolStep(ctx Context, int myparam) error {}
// or... 
func myCoolStep(ctx Context, myparam int, anotherparam string) error {}

Thanks to this, the context can be simplified to contain only getters for context-based parameters.

ctx.GetInt(userID{})

On the other hand, it put a bit more responsibility to users while changing/writing scenarios. The debugging can be a bit harder, too. IMO it's acceptable but I want to hear feedback from you.

[bkielbasa]

the decision has been made - we're doing it!