Search always targets default endpoint

[osma]

At which URL did you encounter the problem?

http://localhost/Skosmos/rest/v1/unesco/search?query=education

What steps will reproduce the problem?

1. Configure a vocabulary that uses a different SPARQL endpoint than the default endpoint set in config.inc
2. Perform a search on that vocabulary

What is the expected output? What do you see instead?

Expected that the search would target the vocabulary-specific SPARQL endpoint. Instead it will target the default endpoint.

I think this is related to the ConceptSearchParameters refactoring. I noticed that with the example REST search above, $params->getVocabIds() returns null.