Deprecate volatile option

[fsmanuel]

Ember 4.0 removed .volatile() on computed(). This PR adds the deprecation to remove it in version 5.0 of this addon.

Tests for ember-4.0, release, beta, and canary are expected to fail.

[fsmanuel]

@MelSumner before we release a new beta version we should merge this to get the deprecation out.

[RobbieTheWagner]

@fsmanuel we should just remove this entirely. I wouldn't worry about deprecating it. We should update all the things to work with latest Ember and not worry about supporting legacy Ember versions IMO.

[fsmanuel]

@rwwagner90 In general I agree. The thing with this addon is that it should probably not be used in new ember apps as the main mental model is about computed properties. In the projects I currently use it I don't know when to migrate to ember version >= 4.0 but I would like to get rid of the super annoying deprecations. That is why I think we should have a version that works for ember < 4.0
The other argument is that we can not just remove features (the volatile option is a feature) just to make it work in new ember versions without thinking about a replacement.

I'm already working on the ember 4.0 version: #717

[RobbieTheWagner]

@fsmanuel yes, but volatile has been deprecated a very long time in Ember. I think we can remove it. Those who want to still use it can just use earlier versions of this addon.

[knownasilya]

Agreed. Could you remove it @fsmanuel? I can merge and release once that's done.

[MelSumner]

@knownasilya I agree with removing it instead of adding a deprecation notice, but should we get it working for 4.0 before doing a new release? WDYT?

[knownasilya]

I meant the next version for the beta. I think there was a few things still left to remove the beta flag.

[fsmanuel]

@rwwagner90 @MelSumner @knownasilya My point is that volatile is a documented option/feature of the addon and if we remove it things will break without a notice. So I thought we deprecate it and add an assert when we remove it.

If you disagree I'm fine with it and we can close the PR and release a new beta version with current master.

I'll continue working on #717 and drop volatile there.

[knownasilya]

@fsmanuel yeah. Let's do that. We can do multiple major versions if we need.