Use client's session to set POC for test, now that we have the capability to do that.

Use a middleware to set the current POC one time per request, and avoid having to look up the stack for the current request in 'get_current_poc'.

Fetch all overrides for a block at one time.

Speed up the lineage computation by doing some caching.

Unused import.

Get field overrides once per user per block.

Streamline configuration.

Fix poc config tuples