bug#42483: 26.1: thing-at-point doesn't recognize org-link urls

[Boruch Baum <boruch_baum@gmx.com>]

One of the features of function `thing-at-point' is recognition of urls,
so I expected it to be able to recognize org-link urls, but that isn't
the case. Here's an example that when yanked into an org-mode buffer
will display the underlined text 'SageMathCell', and when performing `C-c
C-o' (M-x org-open-at-point) will correctly open the url link. However,
`(thing-at-point 'url)' and `(thing-at-point-url-at-point)' evaluate to
NIL.

   [[https://sagecell.sagemath.org/][SageMathCell]]

I was expecting function `thing-at-point-url-at-point' to check if the
mode was org-mode, and if so, to try something like the following

(defun shamelessly-plagiarized-from-org-open-at-point ()
  (interactive)
      (let* ((context
	      (org-element-lineage
	        (org-element-context) '(link) t))
	     (value (org-element-property :value context))
	     (type (org-element-property :type context))
	     (path (org-link-unescape (org-element-property :path context))))
  (message (concat type ":" path))))

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