The app ID for the Ditto instance.
The siteID needs to be an unsigned 64 bit integer >= 0, i.e. either a
regular non-fractional number or a BigInt in the range between 0 and
2^64 - 1 (inclusive). If siteID is 0, Ditto will generate an
appropriate site ID and persist it when needed. Default is 0.
An identity to be used while in development when you want to control the app name and the site ID of the peer.