fixup! Implement a default roster storage
Turn RosterPacker.ItemStatus into an enum

It is already morally an Enum. Replacing it by an real enum gives us
equals and hashCode for free
Implement equals, hashCode for RosterPacket.Item

Will be used for testing purposes.
fixup! Implement support for using RosterStorage
fixup! Implement support for using RosterStorage
fixup! Implement a default roster storage
Add tests for roster versioning
fixup! Ignore roster pushes with invalid from
fixup! Add tests for roster versioning