Trait to check the worthiness of an account.
Trait defining operations for checking if identity-related calls are allowed.
Trait for checking whether a key change is allowed for a given identity.
Trait defining operations for validating identity names.
Trait defining operations for linking identities to accounts.
Trait defining behavior for handling new identities creation.
Trait defining behavior for handling removed identities.
As the weight accounting can be complicated it should be done
at the handler level.