Secure Area Interface: getKeyInvalidated is unclear

[paulbastian]

The description of getKeyInvalidated is very short and unclear, it may benefit from some more detail, e.g.

• by whom is this invalidated
• why
• what are potential use cases here
• how does this effect the other functionality

[davidz25]

We currently have the following in the KDoc for SecureArea:

 * Existing keys in a Secure Area may be invalidated and this can happen
 * on Android if e.g. the LSKF is removed or if a Cloud-based Secure Area
 * is turned down. This is modeled through the [KeyInvalidatedException]
 * being thrown when attempting to use the key. Applications can also use
 * [getKeyInvalidated] to learn ahead of time if a key is still usable.

which I think is accurate but, yea, perhaps a bit too cryptic. Happy to make this more crisp, suggestions?

[paulbastian]

Does this mean a Wallet should request this function for all active Credentials to verify that they are still useable? Is it realistic that this information can be fetched from a Remote WSCD without user authentication, i.e. do we need keyUnlockData?