Filtering the vector store when using RAG

[pieterjanvc]

At the moment all data in the vector store is considered when performing RAG with llamaindex. However, the package has options to set filters to only consider specific files when searching the DB. This might be a useful feature to expose to the admins in ACCORNS so they can link topics with specific files they uploaded. We could even consider finding a way of creating groups of files that admins can create to apply across different topics