Major Description
Currently Solr supports filtering by node types but it's not aware of the node type hierarchy therefore searching for nt:file doesn't expand to searching for nt:base and nt:hierarchyNode for example. So either we make this dynamic (which would be possibly slow) or we leverage synonym expansion and build the synonym file from the node type hierarchy once and use that when indexing/searching, the open problem is how to deal with changing node types.