Add SemigroupK instance for Validated + tests

[aaronlevin]

No description provided.

[aaronlevin]

Similar to my other PR on adding a SemigroupK instance for Xor. The instance requires only that the failure type has a Semigroup constraint.

[ceedubs]

Looks great. Thanks @aaronlevin!

👍, but we should get the build issues figured out before we merge so we don't throw more variables into the mix.

[ceedubs]

It occurs to me that it might also be handy to create a combineK (or perhaps there's a better name when speaking specifically about Validated) method on Validated directly and have the SemigroupK instance simply delegate to it. If we do this we should probably have a scaladoc comment describing how its behavior is a little different than orElse and combine (which wouldn't be a bad comment to have anyway). I'm not saying that you need to feel obligated to do all of this in your PR - just jotting this down before I forget.

[aaronlevin]

@ceedubs since we're waiting for the build stuff to get fixed, I'm happy to update this PR tonight (EU time) with your suggestion :)

[ceedubs]

Closing and reopening to pick up build fixes.

[ceedubs]

👍

At some point I think it would be good for us to follow up on this comment. I'm happy for that to be a separate effort though.

[aaronlevin]

@ceedubs i think it's a good idea, but i can submit another PR with that change. is cats 0.5 about to be released? it'd be nice to get this in there! :)

[ceedubs]

@aaronlevin it is and it would be :). We have a convention of waiting for two 👍s before merging, so that's all we are waiting on for this PR as far as I'm concerned.

[adelbertc]

👍