Improve usability of redirect operation links in node form

I think I'd prefer inline manipulation of all related redirects via AJAX, much like inline entity form.
I suppose a modal would work, too, but I tend to hate those. ;)

I don't think we can actually use IEF directly for this, but certainly we could borrow some ideas/code/approach.

Agreed it'd be nice to make this more slick. Not sure I'll have time to work on this as part of my current gig, but I'll see if I can get them to sponsor a few hours to start making this work.

I'd love input/direction from the redirect maintainers before I get too deep into this.

Thanks!
-Derek

@idebr: how did you make that gif? Can you attach a patch (even if initial and proof-of-concept) as a basis for moving this forward?

Thanks!
-Derek

A little searching showed me how relatively easy this is. Basically, you need this on the link render array:

      'attributes' => [
        'class' => ['use-ajax'],
        'data-dialog-type' => 'dialog',
        'data-dialog-renderer' => 'off_canvas',
      ],

However, when I tried using off_canvas for #2958635: Restore link to add a redirect on node edit forms, I had a problem that after I successfully created the new redirect via the dialog, once the dialog closed and the host entity form took the full screen again, any in-progress changes to the host entity form were lost and it was as-if the whole form was reloaded. :/ Sure, that means the new redirect now appears in the table of redirects, but e.g. in-progress changes to the title, body, whatever are still getting lost. Making this more slick but leaving #1473288: You lose unsaved content, if you add/edit/delete a redirect on node edit form broken doesn't seem worth it. I was hoping this issue would be the clean way to fix that bug. I haven't dug deeply, yet, but that seems like a flaw in the stock off_canvas support. I haven't had time to dive into the code to understand why this is happening, and why something like the "Add another item" AJAX button on multi-valued fields or the behavior from IEF isn't there. Anyone have any quick pointers on this? I'd be interested in helping move this issue forward, but I don't want to sink too many hours into FAPI/AJAX debugging hell to get to the bottom of it. ;)

Thanks!
-Derek

p.s. Should we call this issue dup of #1473288: You lose unsaved content, if you add/edit/delete a redirect on node edit form and move this energy back over there? Seems like they're both trying to solve the same problem.