Introduce an authorization SPI

We need an SPI that can be invoked to authorize state changes in a transaction. The method(s) should make it clear in some way which operation is being authorized, and it must run from the same thread as the thread which instigates the state change.

It must be possible to register an implementation of the SPI when the container starts up or acquires the transaction manager.

The operations that should provide authorization checks include, but are not limited to:

• begin
• rollback
• prepare
• forget
• commit (one or two phase)
• recover

Thanks!