Return false if the message does not contain enough contextual configuration to preemtively
support the given assertion. Otherwise, return true. If false, the PolicyEngine.supportsAlternative
method will not select this policy and will attempt a different alternative.
Example: If the context does not contain login information, an assertion that requires it
could return false to allow the Alternative selection algorithms to try a different alternative.
msg - The contextual message, may be null if no message is in context at this point