Any state change that needs to be signed is first wrapped in this enum and then its serialized.
This is done to make it unambiguous which command was intended as the SCALE codec’s
not self describing. The enum variants are supposed to take care of replay protection by having a
nonce or something else. A better approach would have been to make StateChange aware of nonce or nonces.
There can be multiple nonces attached with a payload a multiple DIDs may take part in an action and they
will have their own nonce. However this change will be a major disruption for now.
Never change the order of variants in this enum