Feat: add a metadata template

[cristianvasquez]

This adds a metadata example to the pipeline template (to be filled in)

#4

[tpluscode]

IMO we don't really understand the requirements for a practical solution and it's too early to add this already to the example workflow

[cristianvasquez]

This is not the prov Metadata step but the 'normal' Metadata, for templates

[cristianvasquez]

However, after second thought, we could arrive at much more generic mechanisms for RDF metadata templates that attach to entities.

Related: zazuko/barnard59#135

Some POCs: https://github.com/zazuko/barnard59-examples-pocs/tree/main/examples

I'll move this to draft

[tpluscode]

However, after second thought, we could arrive at much more generic mechanisms for RDF metadata templates that attach to entities.

Indeed, I was thinking that cube-creator could also take advantage of such a step to provide its metadata instead of the current solution. And then also from other sources such as CI variables or model metadata (WIP with @magdasalatka)

[tpluscode]

Closed in favor of zazuko/barnard59#92