Seeding an already existing external link (URL and link type) to an existing release displays a duplicate. This is not only displayed in a confusing way (MBS-12032) but also leaves a false error message behind even after the user has removed it (MBS-8570).

Rather than forcing all external tools to deduplicate external links before seeding them, it would be very useful if the server would do this automatically, similar to how it does this for label/catno pairs since MBS-13579.

(I have only tested this for the release editor, other entity editors might also be affected.)