[DB] Documents should be related to data sources not projects

[nschenone]

Currently documents are related to projects and not data sources. For example, if I create multiple data sources (vector stores) in a project and try to ingest a document into data source 2 that already exists in data source 1 with the same name, I get a unique name error.

Each of these data sources should be completely separate with their own uniqueness constraints. It shouldn't matter what is in a different data source when ingesting