Skip Libkey lookup for records with multiple DOIs or PMIDs

[jazairi]

Why these changes are being introduced:

Some records can have many DOIs or PMIDs (as many
as 467 in one case). It's probably not helpful
for Libkey to assume that the first identifier
is the best one.

Relevant ticket(s):

• https://mitlibraries.atlassian.net/browse/USE-332

How this addresses that need:

This adds a guard clause to the DOI and PMID
methods that returns nil when multiple identifiers are found. This prevents Libkey from showing an
uncertain fulfillment URL.

Side effects of this change:

Reduction of fulfillment links made available via
Libkey.

Developer

Accessibility

• ANDI or WAVE has been run in accordance to our guide.
• This PR contains no changes to the view layer.
• New issues flagged by ANDI or WAVE have been resolved.
• New issues flagged by ANDI or WAVE have been ticketed (link in the Pull Request details above).
• No new accessibility issues have been flagged.

New ENV

• All new ENV is documented in README.
• All new ENV has been added to Heroku Pipeline, Staging and Prod.
• ENV has not changed.

Approval beyond code review

• UXWS/stakeholder approval has been confirmed.
• UXWS/stakeholder review will be completed retroactively.
• UXWS/stakeholder review is not needed.

Additional context needed to review

E.g., if the PR includes updated dependencies and/or data
migration, or how to confirm the feature is working.

Code Reviewer

Code

• I have confirmed that the code works as intended.
• Any CodeClimate issues have been fixed or confirmed as
  added technical debt.

Documentation

• The commit message is clear and follows our guidelines
  (not just this pull request message).
• The documentation has been updated or is unnecessary.
• New dependencies are appropriate or there were no changes.

Testing

• There are appropriate tests covering any new functionality.
• No additional test coverage is required.

[jazairi]

I believe the failed deployment is due to a service degradation affecting Actions, but will confirm when that's resolved.

[JPrevost]

@jazairi would you mind rebasing to see if the tests and deploy fix themselves as expected?

[coveralls]

Pull Request Test Coverage Report for Build 21637796633

Details

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.003%) to 98.123%

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Totals
Change from base Build 21631890289:	0.003%
Covered Lines:	1307
Relevant Lines:	1332

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💛 - Coveralls

[jazairi]

@JPrevost All set.