Migration guide v4.2.0

Import additional information about CGMES boundaries as extensions

Since this version, new extensions CgmesDanglingLineBoundaryNode and CgmesLineBoundaryNode have been added to retrieve additional information about CGMES boundaries. If you are using a custom IIDM implementation, you will have to implement these extensions and their adders and create providers for your custom adders' implementations if you want to continue using the CGMES import.