[rdf] Add rdf adapter regid parameter on add_entity_to_graph
Function add_entity_to_graph
in cubicweb.rdf
adapts an entity using its "rdf"
adapter and adds its to a rdflib Graph.
In some projects (e.g., FranceArchives, EAC cube), we deal with two different rdf adapters: one for schema.org metadata with regid "rdf.schemaorg", one for content negociation (regid "rdf" in francearchives and "rdf.rico" in eac).
We had to redefine the add_entity_to_graph
function in the projects to use the adapters whose regid is not "rdf"