Do not require description for license entity

[stain]

"Check this crate" will bail out if the license points to a contextual entity without description.

This is not a strict requirement or SHOULD from https://www.researchobject.org/ro-crate/1.1/contextual-entities.html#licensing-access-control-and-copyright, rather it says informally:

The @id of the license SHOULD be its URL (e.g. a Creative Commons License URL) and, when possible, a summary of the license included using the description property.

This issue suggests to remove that restriction.

[ptsefton]

Yep - will fix.

[ptsefton]

The link to the spec you provided @Stian is not for the root dataset (this is where that is specified: https://www.researchobject.org/ro-crate/1.1/root-data-entity.html#direct-properties-of-the-root-data-entity) but the behaviour is still wrong. We probably need to tighten up the wording as it's a bit unclear whether a simple textual value is OK - eg "CC BY-NC 4.0"

[ptsefton]

Looks like the tests currently in the ro-crate library are correct and should not be bailing out as long as there a value for license - I will update the distribution when I have looked at other bugs and get you to retry @stain

[ptsefton]

I have pushed a new version of the library and the rendering code - can you check please @stain.