An on-disk Episteme.Database.Backend, for a database that should
survive past the owning process (or the VM) -- same {name, arity}-keyed
:set shape as Episteme.Database.Backends.Ets, backed by :dets
instead. Requires a :file option (a binary or charlist path) on
Episteme.Database.new/1; :table names the DETS table itself
(defaults to a name derived from :file, so two databases opened
against different files don't collide).
:dets's own limits apply -- single Erlang node, roughly 2 GB per
table, and no coordination for concurrent writers beyond what :dets
itself serializes internally. This is "an embedded database that
persists across restarts," not a substitute for a real multi-writer
datastore. Writes are only guaranteed durable after sync/1 (:dets
itself flushes periodically, but not before every single insert).