Add ID Resolver

[elado]

Methods like destroy require id, and can't get the actual model as a parameter.

A resolver would get the idAttribute from the model. For example:

Article.destroy(article)

will access article[Article.idAttribute] to find ID in case this is an object.

Thoughts?

[jmdobry]

Yes, there are two methods (at least) that support the id or instance API. I should probably make the API more consistent and use it everywhere or nowhere.

[elado]

👍 thanks!