Remove Nulls Deeply

[joeydong-stripe]

Summary

Improve the NSDictionary / NSArray remove nulls helpers to scan deeply instead of only at the first level.

Motivation

Nulls are particularly difficult to work with in any situation so just filter them out everywhere.

Testing

Updated unit tests.

[bg-stripe]

hmm. my guess is there probably aren't many users at the intersection of

• use allResponseFields
• explicitly check for NSNull in a nested dictionary, and don't also check for nil

seems like a worthwhile improvement to me, and worth the small risk of a subtle break as long as we call it out in MIGRATING

[joeydong-stripe]

I guess the trickiest thing you can end up doing is something like:

if (card.allResponseFields[@"metadata"][@"username"] != nil) {
    // Do something without actually checking the value of metadata.username
}

[joeydong-stripe]

r? @bg-stripe

[bg-stripe]

lgtm!

[joeydong-stripe]

Oops forgot too add an entry to the CHANGELOG