Multiembedding support on DB

Our current assumption is that models often produce a 1v1 mapping to embeddings but that is not the case .... for several models e.g [insightface](https://github.com/deepinsight/insightface), a single input can produce N embeddings (depending on how many faces are in the image)

Short of duplicating the metadata (which seems like a very bad idea as that would be O(N) for space usage within the DB), we have no apparent way at the moment to make this play nicely with the DB.