transactionVersion property
All existing dispatches are fully compatible when this number doesn't change. If this
number changes, then spec_version
must change, also.
This number must change when an existing dispatchable (module ID, dispatch ID) is changed, either through an alteration in its user-level semantics, a parameter added/removed/changed, a dispatchable being removed, a module being removed, or a dispatchable/module changing its index.
It need not change when a new module is added or when a dispatchable is added.
Implementation
final int transactionVersion;