Add support for grouping conditions with and/or operators

[DiogoDoreto]

In our project we would benefit from extra conditions for our Story's controls, to better match our more complex polymorphic component parameters.

Please check the new tests for example usage.

[kasperpeulen]

cc @tmeasday @shilman

[shilman]

Cc @kylegach

[kylegach]

Nice work, @DiogoDoreto!

The API is as straightforward as I can imagine it being. I recommend that we only document one level of nesting, though, even if it's implemented recursively as it is here.

That said...

to better match our more complex polymorphic component parameters

I wonder if there's something better we could offer for this use case, that wouldn't require manually authoring a bunch of complex conditions. Whatever that is, it could likely be implemented as an auto-generation of this feature. So this PR is still valuable.

[DiogoDoreto]

Thanks, @kylegach!

Regarding your last point, what we really thought about initially was to have the options of a control to be dynamic and based on the values of other controls. Since this was a major change from the current requirement of being statically defined we tried to avoid it. The current solution is to multiply the number of controls with pre-calculated options and predefined rules for visibility — where multiple conditions come in handy. And yes, we are autogenerating those :)

[darkgrayknight]

This would be great. Is anyone looking at this PR and going to see about merging it in?