Support file based autocomplete fields, other than the existing namespace based retriever. #798
Description
Is your feature request related to a problem?
When a user is asked to fill in HealthDCAT-AP based metadata, there are a number of fields (e.g. language) that require values from a controlled vocabulary. Having a dash:editor dash:URIEditor is error-prone and asks a lot from a non-technical user. The current autocomplete settings either require a SPARQL endpoint, or require the namespace to contain the type and the values (see RdfEntitiesNamespaceRetriever). For dct:language, the type is dct:LinguisticSystem but the values should come from the EU Vocabularies Languages Named Authority List.
What solution you'd like?
An option like the current SPARQL based autocomplete setting, but for file-based vocabularies. There is logic for resolving these values in the RdfEntitiesNamespaceRetriever already, adding an extra parameter there or a separate implementation of a RdfEntitiesRetriever with the corresponding form in the settings would be great.
What alternatives have you considered?
Not all controlled lists are available in a SPARQL endpoint. A workaround could be loading (and maintaining) the lists in a specific triplestore, but that comes with a maintenance burden.
Additional context
No response