allow editing the UUID in a resource link after it has been created

[alicewriteswrongs]

CKEditor's link package support editing the url for a link by clicking on it:

We'd like to support something similar for resource links. This should probably re-use the resource picker because we don't expect that the user knows the UUID for random resources. A basic idea for how this works could be:

• user clicks on a resource link in the editor
• user gets a menu like the one above with an 'edit' button
• clicking the edit button opens the resource picker with 'Update link' as the confirm text for the dialog
• selecting a resource and clicking 'update link' updates the uuid attribute on the text

I think we can do this by modifying the ckeditor link form that pops up to call a function that we put onto the editor config.

[alicewriteswrongs]

I'm unassigning myself - if this is something we still want to do perhaps @ChristopherChudzicki would be in a good position to work on it. I think that doing so will involve further modification to our 'resource link' fork of ckeditor's link package, because we'll need to figure out some way to either 1) hijack the link URL/href editing functionality in order to add a UUID selector or something or 2) figure out a good way to render our own React component which implements that functionality.

[alicewriteswrongs]

I also just realized I opened an issue over in our ckeditor fork, here: mitodl/ckeditor5#6 so there's that!