One resource can be assigned to multiple work center but cant assign a resource instance

Summary:

One resource can be assigned to multiple work center but can't assign a resource instance to multiple work center.

Content (required):

For example, labor resource instance employee A is part of technician resource and at the same time the same employee A is part of Operator resource, but system doesn't allow the same resource instance in more than one resource.

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Code Snippet (add any code snippets that support your topic, if applicable):