stepIndex property
Progressions define their levels in "steps". Since the last step may be repeatable, the user may be at a higher level than the actual Step achieved in the progression. Not necessarily useful, but potentially interesting for those cruising the API. Relate this to the "steps" property of the DestinyProgression to see which step the user is on, if you care about that. (Note that this is Content Version dependent since it refers to indexes.)
Implementation
@JsonKey(name:'stepIndex')
int? stepIndex;