Added omittable steps

[ercsctt]

Issue reference: #43

Please let me know if there's anything I can change here, I've tried to implement this in the most elegant way without having to modify a bunch of logic. I needed this for a personal project, and it works fine as is (afaik), but if there's a better way of doing this without rewriting the entire wizard logic let me know 😂

[ksassnowski]

I took a quick glance at the changes and I think I agree with the overall design. I think availableSteps needs to be cached somehow, so we aren't looping over the steps over and over again. Especially since the omit method of a step can contain arbitrary code (like a network call). I also think that we should pass the current request to the availableSteps method.

I'll have a closer look at this in the next few days

[ercsctt]

Unsure if caching would work in this case, as the point of availableSteps is to get any available steps at that time, and be reactive to showing different steps based on the result of omit.

[ksassnowski]

I meant caching for the current request. For instance, both the summary and nextStep methods currently call availableSteps. Since the response renderers will likely want to call the summary method, we'd essentially be doing double the work for no reason.

I think availableSteps should be lazily calculated and return the cached value if it has already been computed before. Might have to think about invalidating the cache, i.e. force a recompute, after the wizard's data has changed.

[ercsctt]

Yep I get that, okay so out of sheer laziness I've used the spatie/once package for this purpose as it does a pretty good job at this with little code change. It's reduced the calls to omit from 3 to 1 in a single request.

[Wulfheart]

This feature would be really nice indeed.

[ksassnowski]

I’ll look at this once I’m back from vacation

[ksassnowski]

I've made couple of small changes to the PR. Most notably, I implemented the memoization of the available steps myself as I would rather not pull in a whole other dependency just for that. I also added a few extra tests to for the wizard and wizard repository.

Other than that, looks good to me. Thanks for the contribution!