In the tab "Citation information, if there is no DOI, offer a "link" to determine the DOI.

1. The text "The entry does not have a DOI" should be replaced by the functionlity at the tab "Citation relations" (See PR https://github.com/JabRef/jabref/pull/13539)\
   
2. When clicked, the text should change to "Looking up DOI..."
3. If no DOI found, notifiy users "No DOI found" and change to initial state.
4. If DOI found: Use it for lookin up information in this tab

Add following paper to JabRef:

@InProceedings{Edwards2004,
  author    = {S. H. Edwards},
  booktitle = {Proceedings of the 35th SIGCSE Technical Symposium on Computer Science Education},
  date      = {2004},
  title     = {Using software testing to move students from trial-and-error to reflection-in-action},
  pages     = {26--30},
}

Click on "Citation information"

Now switch to "General" and click "Look up DOI"

See that a DOI is dermined:

Then, switch to onther entry (or create a new one). Swich back.

Then, "Citation information" should work (if there was no network error)