input validation bug leads to duplication of items built from DOIs

[stuartyeates]

Describe the bug The check to see whether a DOI is in wikidata needs to have the same domain as the code to generate the item.

To Reproduce Steps to reproduce the behavior:

1. Go to https://scholia.toolforge.org/doi/https://doi.org/10.3390/MICROORGANISMS12071299
2. Create the item
3. Notice that the DOI already exists
4. See error

Expected behavior https://scholia.toolforge.org/doi/https://doi.org/10.3390/MICROORGANISMS12071299

Should redirect to

https://scholia.toolforge.org/doi/10.3390/MICROORGANISMS12071299

Or at least have the same behaviour

[fnielsen]

This is probably due to the current load on the Scholia web app #2727. Our error handling should be better.