RFC API adjustments for Versioned

[maxime-rainville]

While rewriting the versioning doc (#150) there's a few things that looked a bit weird to me.

I think we should consider implementing the following changes for SS5.

• deprecate doRevertToLive because it does more less the same thing as rollbackRecusrive
• deprecate canRevertToLive and create a new canRollback
• deprecate doArchive and encourage people to use a straight delete instead
  • Maybe add a new deleteRecursive/deleteSingle
• deprecate doUnpublish and replace with a unpublishSingle and unpublishRecursive
• deprecate either Versions or allVersions. Versions is an alias for allVersions.
• We don't currently have a way of getting only archived records. If you use get_including_deleted, you'll get draft version as well. I would suggest either having a dedicated method (e.g. get_archived) or updating get_by_stage to support an ARCHIVE stage.
• Renaming the "Stage" stage to "Draft". It's really confusing in the doc when we refer to the "Stage" stage

[NightJar]

Adding features and deprecation (but not removal) is achievable in a minor release, no? Is there more to this that makes you think it needs to wait for SilverStripe v5?

[maxime-rainville]

Adding the deprecation warnings and tweaking the function names could be done right away, although there would be some work involved in moving our existing code from the deprecated API.

The last bit (Renaming the "Stage" stage to "Draft") would not be a breaking change and could not be done in a minor release.

[robbieaverill]

The last bit (Renaming the "Stage" stage to "Draft") would not be a breaking change and could not be done in a minor release.

This might assume that people use the constants for the value of the stage, I don't think that's usually the case from what I've seen. From memory the constants are relatively new. I think this would be a damaging change to make without B/C support in 4.x