SYSML2 — Semantic constraint for target of AssignmentActionUsage is missing

In 7.16.9 Assignment Action Usages, at the beginning of the second text paragraph, it states

If the target expression of an assignment action usage is omitted, then the target is implicitly the occurrence owning the assignment action usage.

However, there is no semantic constraint to enforce this (see 8.3.16.5).

Update library model for assignmentActions

The intent of the default described in 7.16.9 can be achieved by defaulting the first parameter (target) to that in the body of Actions::assignmentActions. Note that this has to be done in the usage, because that is only defined for Features.