Provide feedback about external references when reuse element is drag&dropped from reuse library into AF3 project
Currently, the reuse plugin can already detect external references inside a reuse element (e.g. used UserDefinedFunctions inside a Component with Code Specification). This is displayed when adding or updating a reuse element inside a reuse library or when updating a reuse element in the project from within a reuse library.
The only case where this is currently not displayed is when a reuse element is newly reused (drag&drop from the reuse libraries in the model elements view into the project). This should be realized, too.
Connected to #4125 (closed)
Might be not needed anymore or must be changed if #4150 is realized