VerifKey
    ident    Text
    instance InstanceId
    expires  UTCTime Maybe
    public   ByteString
    sharer   RemoteSharerId Maybe

    UniqueVerifKey ident

VerifKeySharedUsage
    key  VerifKeyId
    user RemoteSharerId

    UniqueVerifKeySharedUsage key user

RemoteSharer
    ident    Text
    instance InstanceId
    inbox    Text

    UniqueRemoteSharer ident

Instance
    host Text

    UniqueInstance host