create ER diagram, refactor to conform to diagram, simplify session management

WorkoutsPlus/Debug/DebugList.swift

@@ -34,7 +34,7 @@ struct DebugList: View {
 						Section(header: Text("WorkoutItems")) {
 								ForEach(workoutItems) { workoutItem in
 										VStack(alignment: .leading) {
-												Text("\(workoutItem.name), pos: \(workoutItem.position), reps: \(workoutItem.reps)")
+												Text("\(workoutItem.name), pos: \(workoutItem.position), reps: \(workoutItem.plannedReps)")
 												Text(workoutItem.id.uuidString)
 														.font(.system(size: 12, weight: .bold))
 														.fontDesign(.monospaced)