fix: check if fields present in author before adding mention

[ewan-escience]

Prevent undefined authors in mentions

Changes proposed in this pull request:

• Prevent Crossref mentions form having undefined authors by checking if the fields are present first
• Try to use the name field if either given or family is missing
• Apply the same logic to the Crossref scraper

How to test:

• docker compose down --volumes && docker compose build --parallel && docker compose up --scale data-generation=0
• Create some page, add a mention with DOI 10.1103/physrevd.108.072003
• Check the last author, this should be ATLAS Collaboration
• The words undefined or null should not be part of the authors
• Run the mention scraper: docker compose exec scrapers java -cp /usr/myjava/scrapers.jar nl.esciencecenter.rsd.scraper.doi.MainMentions
• The last author should be unchanged
• The words undefined or null should not be part of the authors

Closes #1208

PR Checklist:

• Increase version numbers in docker-compose.yml
• Link to a GitHub issue
• Update documentation
• Tests

[sonarcloud]

Quality Gate passed for 'scrapers'

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[sonarcloud]

Quality Gate passed for 'rsd-frontend'

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[dmijatovic]

Nice work!