ArchiMate Exchange Format - handle sourceAttachment and targetAttachment

### Description

Archi doesn't support source and attachment points from the ArchiMate Exchange Format on connections. It might be possible that when importing an exchange file to add bend points to create a similar effect.

### Example

Exported from:

After imported:

No source files or tests are named. Start by reproducing the import using an ArchiMate Exchange Format connection with sourceAttachment and targetAttachment, then trace the import handling for connections and bend points. Done means imported connections preserve the attachment-point effect shown in the example.

Written by the indexing model from the issue text.