keysThatFoldedOntoOneFilenameAddressDistinctEntries

Five distinct keys the legacy filename mappings folded onto one file.

Regex("[^a-zA-Z0-9_-]") → "_" (JVM) and Char.isLetterOrDigit() (Apple) both sent a.b, a/b, a b and a:b to a_b — which is itself a key. So four of the five writes below destroyed a value written under a different key, silently, and every read but the last returned another key's bytes. There is no listing surface on DurableStore through which a caller could have noticed.