@API(status = API.Status.STABLE)
    public @NonNull Permission commandPermission() {
        return this.permission;
    }
Returns the permission required to execute the command.
<p>
If the sender does not have the required permission a {@link org.incendo.cloud.exception.NoPermissionException}
will be thrown when parsing the command.

@return the command permission
cloud-core/src/main/java/org/incendo/cloud/Command.java