private static String targetFieldAsString(String targetFieldName, DocumentReference reference) {
        return "Field '" + targetFieldName + "' via reference field '" + reference.referenceField().getName() + "'";
    }
Iterates all imported fields from schema parsing and validates and resolves them into concrete fields from referenced document types.

@author geirst
config-model/src/main/java/com/yahoo/schema/processing/ImportedFieldsResolver.java