Fix I18n lookup for enum values in nested select fields

[Fs00]

This PR accomplishes the same as #1227, albeit with a more focused approach.
When constructing the key for looking up the localized enum value, we now use ActiveModel::Name.i18n_key instead of object_name, which returned something like user[posts_attributes][0] in case of nested forms.
I've added a test that reproduces the exact scenario that triggered the fixed bug (#1151).

Bonus: I've added a commit to update Formtastic version in Gemfile.lock (it was still 4.0.0.rc1).

Fixes #1151
Supersedes #1227

[Fs00]

@mikz @justinfrench Any plans to review/merge this in the near future?

[mikz]

Sorry, looks like I'm not subscribed to new issues 🤦🏻‍♂️

I think this looks great! It does not break tests, it adds a new one, it is very clear in what it does.

Great fix 👍

[Fs00]

Thanks!
Will there be a new release anytime soon? I think that there have been some interesting fixes since 4.0.0 that may be worth a patch release.

[mikz]

@Fs00 indeed, but as we are not doing many there is always some element of fear included :)
I'd recommend pointing bundler to the git repo in the meantime.

[Fs00]

Oh well, less changes, less fear! 😄 I think that waiting will only make things more risky and difficult.

Anyway, I cannot point Bundler to the Git repo, since I use this gem in an enterprise environment where dependencies can't be pulled from the "outside world". I'll wait patiently 🤷‍♂️