Allows creating a FullViewingKey from a given SpendValidatingKey and
from the other components which can be randomly generated, but there
may be some utility in specifying them too like supporting FROST backup
schemes that don't centralize spend authority
builds atop #428
Allows creating a FullViewingKey from a given SpendValidatingKey and from the other components which can be randomly generated, but there may be some utility in specifying them too like supporting FROST backup schemes that don't centralize spend authority
closes #431
see related #430