Semantic clustering of propositions

[carlgieringer]

This could be fine-tuned by the relations and votes from #13. Similar infrastructure here could support semantic search of propositions.

[carlgieringer]

• https://www.pinecone.io/pricing/

[carlgieringer]

RDS now supports pgvector at Postgres 15.2 and up:

• https://aws.amazon.com/blogs/database/building-ai-powered-search-in-postgresql-using-amazon-sagemaker-and-pgvector/
• https://github.com/pgvector/pgvector