fix: dataType.delete() should use docId not versionId

[gmaclennan]

Description

Reading through #420 made me realize that I think our current delete() method does not make sense. Trying to "delete" an arbitrary version of a doc doesn't actually do anything unless it is a "head". It will actually create a fork, which is kind of confusing.

e.g. we have a doc with docId X, created with versionId A. It is then edited so we have version B. Now a user tries to delete version A. They will create a new version C, and we now have two "heads" or "forks": B and C.

I think the delete method should actually accept the docId, since what you actually expect from deletion is that the document is no longer returned from getMany(). The delete function should:

1. Get the existing doc for that docId, and get the versionId
2. Check the forks property, and also get the existing doc(s) for those forks, to get the versionIds
3. Create a doc with deleted: true that has links with the versionIds above.
4. For the document data that is written to the delete doc, use the value from (1) (e.g. the doc that would be returned from dataType.getByDocId(docId).

@achou11 @tomasciccola thoughts or comments?

[gmaclennan]

This could raise the question, "how do I delete a fork", which you do as:

const obs = await project.observation.getByDocId(docId)
const merged = await project.observation.update([obs.versionId, ...obs.forks], valueOf(obs))

Could look at creating a helper for this in the API if needed once we introduce a UI for managing forks.

[achou11]

yeah i think this makes sense. So basically:

• DataType.delete() is reserved for deleting the latest locally known version of a record
• if needed, you could technically use DataType.update() to delete an older version or delete a fork?

[gmaclennan]

yeah, although "deleting an older version" and "deleting a fork" doesn't really have a clear meaning.