Possibly incorrect warning in renku template validate

[RichardJActon]

Describe the bug

'Manifest warnings' are produced by the renku template validate command when it is run on the main and community templates repo. I'm not sure if this is a bug with the validation or the manifest files using an incorrect key - the manifest clearly work so I suspect the former.

To Reproduce clone the https://github.com/SwissDataScienceCenter/contributed-project-templates repo and run renku template validate

Manifest Warnings: Template 'aiida' should use 'id' attribute instead of 'folder'. Template 'aiida' variable 'archive_url' uses old string format in manifest and should be replaced with the nested dictionary format. Template 'python-minimal-streamlit' should use 'id' attribute instead of 'folder'. Template 'desktop' should use 'id' attribute instead of 'folder'. Template 'qgis' should use 'id' attribute instead of 'folder'. Template 'matlab' should use 'id' attribute instead of 'folder'. Template 'Renv' should use 'id' attribute instead of 'folder'.

Run environment (please complete the following information):

• renku-python version 1.9.3
• Python version 3.8.10
• local terminal