postgresql: Make the objstorage argument optional
When unset, defaults to a NoopObjstorage. This can be useful for
testing, and it allows to use the swh db init storage
without
a configuration file (see swh-core!359 (merged) ).
When unset, defaults to a NoopObjstorage. This can be useful for
testing, and it allows to use the swh db init storage
without
a configuration file (see swh-core!359 (merged) ).