BridgeDB has a table called BlockedBridges in its SQLite database. The table is empty and currently unused but we are extending it over at legacy/trac#34154. BridgeDB already has code to deal with bridge blocking (e.g., [here](https://gitweb.torproject.org/bridgedb.git/tree/bridgedb/bridges.py?id=2ccf7ef9dee07c0d645a5dfed5b099678c243fc5#n936)) but we still have to make it process BlockedBridges and take it into account when handing out bridges.