When the user enters a DOI, the system should query the DataCite API to determine if metadata already exists. If it does, the user should be prompted to auto-fill the metadata form. The user must be able to review, edit, and adjust version information before saving, without creating duplicates.

User Story

• As a user entering metadata, I want the system to detect existing DOI metadata and offer to auto-populate the form so I save time and avoid duplicates.
• As a user, I want to choose whether to apply the prefill or manually enter metadata.

Acceptance Criteria

• DOI entry triggers a lookup via the DataCite API.
• If metadata exists, a modal/pop-up prompts the user whether to prefill the form.
• On confirmation, mandatory and optional metadata fields are populated.
• The user can edit all prefilled fields.
• The user can adjust the version before saving.
• Saving does not create duplicate entries for the same DOI.
• If no metadata exists for the DOI, the user can proceed manually.
• Tests verify correct behavior for known and unknown DOIs.