Download: Seqera container support - Patch 1

[MatthiasZepper]

This PR extends the tests so that Seqera Container support is tested for. It also tweaks the symlink function to support the unconventional registry that Seqera Containers uses.

This is a basic patch. It does neither add oras:// support nor does it fix the issue with the container priority resolution (#3179). For modules using Seqera containers, nf-core download will always download both containers, the native Singularity one and convert the Docker container to Singularity as well.

PR checklist

• This comment contains a description of changes (with reason)
• CHANGELOG.md is updated
• If you've fixed a bug or added code that should be tested, add tests!
• Documentation in docs is updated

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 4 lines in your changes missing coverage. Please review.

Project coverage is 75.34%. Comparing base (354311d) to head (32a7e6b).
Report is 17 commits behind head on dev.

Files with missing lines	Patch %	Lines
nf_core/pipelines/download.py	80.00%	4 Missing ⚠️

Additional details and impacted files

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[pinin4fjords]

Thank you for this resolution, we appreciate you :-)