Outline runs as an unprivileged user in the image (``nodejs`` since
1.10.0, ``root`` up to 1.6.1) while the datastore is provisioned by
``root``. Without realignment the application cannot write its
``uploads``, ``public`` and ``avatars`` buckets, so every attachment
upload fails with "Permission denied writing to ... Check the host
machine file system permissions". This was seen on elabore.coop
after the 1.6.1 to 1.10.0 upgrade.
The ``init`` hook now reads the image's ``Config.User`` and chowns the
datastore to that user, skipping root-based images. It is idempotent
and version-agnostic: the realignment also covers buckets added by
future Outline versions.
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