AC:
* //wbeditentity// allows adding and editing of Lexeme forms per the same business logic implemented in //wbladdform// & //wbleditformelements//
* //id// is used instead of //formId// to identify forms inside //wbeditentity// (`forms[]{ id: ... }`), //wbladdform//, //wbleditformelements//
Info:
* Rename of //formId// to //id// was done for //wblremoveform// in T189673 / https://gerrit.wikimedia.org/r/#/c/422099/
** https://gerrit.wikimedia.org/r/#/c/424333/ fixed a bug, causing problems when removing forms at the same time as performing other entity edits ("change ops")
* //RemoveFormConstraint::many()// describes (parts of) a Lexeme entity, not only the forms part as the name suggests. To allow for more actions (add, edit), this should be split - e.g. a collection in //RemoveFormConstraint::many()//, and a //LexemeConstraint// that describes the properties and different (action) constraints for them