fix: worker specifier can be a string or an URL instance

[jerome-benoit]

PR Checklist

• Please ensure title follows conventional commits.
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Does this PR introduce a breaking change?

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closes #94

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

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