Deleted classes in forms with "change selection"

[hauschke]

Describe the bug
When editing entries via e.g. "Reviewer of" and changing the selected entity, the old connected entity loses all its class assigments.

To Reproduce
Steps to reproduce the behavior:

1. Go to a person's profile, switch to the "Service" tab.
2. Add an article via "Reviewer of".
3. Open the created article in a different browser tab.
4. Go back to the person's profile.
5. Edit the reviewed article.
6. Change it to a different article.
7. Open the first article that was created. All class assignments of the article are deleted. Not even owl:thing is kept.

Expected behavior
The not connected article should not be touched at all, only the connection to the reviewer should be deleted.

Screenshots

Additional context
This behaviour seems to affect all forms. This is a deeper issue and most likely a blocker.

[brianjlowe]

AddRoleToPersonTwoStageGenerator.java has "?existingRoleActivity a ?roleActivityType ." on line 223 in getN3ForExistingRoleActivity(), which doesn't look like it belongs.

Additionally, the existing year range isn't displayed on the form when editing an existing role, because addRoleToPersonTwoStage.ftl calls @lvf.printYearField, which can't render the year correctly because the year variable isn't assigned. The HTML supplied in htmlForElements['startField'] and htmlForElements['endField'] does contain the existing value, but the label for the fields is wrong.

[tawahle]

We have noticed the behaviour also in several customized forms, where in the type selector classes are hard coded literals and in the corresponding freemarker template the type selector is like activityTypeLiteralOptions?keys. These forms are not based on AddRoleToPersonTwoStageGenerator, but the behaviour is the same. After running changeSelection and assigning a new class, the old entity loses all of the classes.