AccessWalk
data class AccessWalk(val schema: String, val heads: Map<Int, Long>, val cursor: String? = null, val walked: Long = 0, val completed: Boolean = false)
The walk of one aggregate type, as its log records it (AccessWalks.walk): schema, the type's access schema it stamps with; heads, each partition's head when it was claimed, which bound the streams it stamps (later ones are the follower's); cursor, the page of aggregates it is past (null: none yet); walked, the aggregates it stamped; whether it is completed.