* helm: keep the filer db credentials across uninstall and install
The db secret is kept on uninstall (`helm.sh/resource-policy: keep`), but it
is a pre-install hook, and Helm deletes an existing hook resource before
creating it again. The next install therefore wrote a new random password
and reset the user to YourSWUser, so the filer could no longer log in to a
database set up with the old ones, including credentials edited into the
kept Secret.
The template now reads the existing Secret with lookup and reuses its user
and password; a first install still generates them as before. A kind step
in helm_ci.yml installs, edits the Secret, uninstalls, installs again and
checks both values.
* helm: README, the db secret is kept and reused across a reinstall
* helm: make the db secret hook-delete-policy explicit
before-hook-creation is Helm's default for hook resources, but spell it
out so the reuse contract is obvious: lookup reads the kept Secret at
render time, the old copy is deleted before the hook recreates it, and
the stored credentials carry over.
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Co-authored-by: Chris Lu <chris.lu@gmail.com>
