cubicweb-seda #13008700 use a custom language rather the pref/alt label for SEDA schemes [validation pending]

currently, we've extracted out of SEDA some vocabularies. On export, we've to insert the 'prefLabel' of the related concept in an unspecified language, because in most case we want a string value, not an unambiguous URL. This is weak, we could probably use prefered label using a SEDA2 language. This will also ease alignment with previous SEDA version (only use different 'translations' rather then scheme alignments).

priorityimportant
typeenhancement
done in0.4.0
load left0.000
closed by#9d17d614e836 [profile gen] Import vocabularies using a seda2 language that takes precedence during export
patch[profile gen] Import vocabularies using a seda2 language that takes precedence during export [applied]