Metadata Plugin: Unable to see the License linked

**Summary**
As reported by @karinholm via HotJar.
She browsed a morphology in public/sscx (prod) and was presented with the following Metadata plugin:


The License appears clickable. But opening it, you get an HTTP 404:
https://bbp.epfl.ch/neurosciencegraph/data/licenses/97521f71-605d-4f42-8f1b-c37e742a30bf

**Proposed Fix**
- if the license is in the resource payload, present the name/label
- if we have an ID,
- if the resource is Nexus managed: fetch the resource and present the name/label. Clicking the label opens the resource panel for that resource. In some cases, there are Files attached to License (see the above license in public/sscx).
- if the resource is outside our Nexus deployment (e.g. https://creativecommons.org/licenses/by/4.0/), present a link to that URL.