The journal is implemented as an ever extending file which contains variable length records
that describe mutations to be applied to various objects. The journal file consists of
blocks, with a checksum at the end of each block, but otherwise it can be considered a
continuous stream.
An object store supports a file like interface for objects. Objects are keyed by a 64 bit
identifier. And object store has to be backed by a parent object store (which stores metadata
for the object store). The top-level object store (a.k.a. the root parent object store) is
in-memory only.
StoreObjectHandle is the lowest-level, untyped handle to an object with the id [object_id] in
a particular store, [owner]. It provides functionality shared across all objects, such as
reading and writing attributes and managing encryption keys.
The mode of operation when setting extended attributes. This is the same as the fidl definition
but is replicated here so we don’t have fuchsia.io structures in the api, so this can be used
on host.
StoreInfo stores information about the object store. This is stored within the parent object
store, and is used, for example, to get the persistent layer objects.