'keyspace' option support on STARTUP message

Most of the drivers provide a way to bind a keyspace to a Client/Session and subsequently its connections, i.e. in the java-driver:

Session session = cluster.connect("mykeyspace");

Currently to bind keyspaces to connections that drivers need to issue a USE <keyspace> query and keep track of which keyspace is bound to a connection. This is non-trivial to manage and this has been a source of quite a few bugs in the drivers.

It would be really nice if in a future protocol version that the STARTUP message supported an option to provide the keyspace to bind a connection to. This way no separate USE <mykeyspace> request needs to be issued.

If the keyspace is provided in this way, it could also be a nice consideration to make the keyspace bound to the connection unchangeable.