Fixed snapshot behavior with nested keys

[SergeAstapov]

@snewcomer I would need some help/advice how to update restore() method.

In v2 branch of ember-changeset, _changes object was stored as a map/hash with keys in format foo or foo.bar.baz.

validated-changeset stores _changes in format like

{
  foo: {
    bar: {
      baz: 'abc'
    }
  }
}

Because of that changes I'm not sure what would you consider the most efficient way of restoring Changeset from snapshot.

The new test #restore restores a snapshot of the changeset with nested values has been created and it currently fails as no changes to restore() have been made.

[snewcomer]

@SergeAstapov Quick comment - one of the main motivations in the original rewrite was to store the keys in a nested format internally so as to easily iterate over the object. (I can/should explain more though)

adopted-ember-addons/ember-changeset#379

[SergeAstapov]

I see, thanks explanation @snewcomer! I'll try to work on this PR and rewrite implementation so that snapshot produces nested format and restore uses it.

[bartocc]

I found this PR and issue #25 while trying to migrate my codebase from ember-changeset-validations 2.x to 3.x.

I get the You attempted to update _changesonchangeset:[object Object], but it had already been used previously in the same computation error.

This happens because if first check {{this.changeset.isDirty}} in a template and later do this.changeset.restore(aSnapshot). My snapshot does not have nested keys though…

Should I consider that restore is broken at the moment in validated-changeset ?

[snewcomer]

@bartocc Here is a chain of PRs I implemented to solve the case where someone calls .validate() on render (we read ERRORS then write them all in one computation...that is a problem). It sounds like this is the same case. We would need to develop a CHANGES_CACHE as well; however, I found it a bit difficult. One option is to change around your flow so that restore doesn't get called in the same render step (likely when rendering a page). Mind sharing the snippet on where you are calling restore?

adopted-ember-addons/ember-changeset#604