v3.4.0

Added

• Selectable webhook payload format. The webhook is no longer tied to one JSON shape.
  Besides JSON (full status) (unchanged default) it can now post a Microsoft Teams
  adaptive card — the message envelope an incoming webhook / "post to a channel when a
  webhook request is received" workflow expects — or a short, human-readable plain text
  status (text/plain). Each format is one entry in a table in app/notify.py, so further
  target systems are a table row rather than new code.
• Severity filter for notifications. A new Send from level setting decides which
  events reach the webhook at all: all events, warnings and critical (new default), or
  critical only. Everything below the threshold still goes to the event log.
• "Send test notification" button in the notification settings: posts a sample message
  with the values currently entered — without saving first, and regardless of the severity
  filter — and reports the HTTP result (POST /api/test/webhook).

Changed

• Info events are no longer sent by default. Existing installations move to the new
  warnings and critical default and therefore receive fewer messages; set the filter back
  to All events (including info) for the previous behaviour.
• Host …: shutdown sent and Host …: shutdown aborted are logged as warnings instead
  of info — an executed or withdrawn shutdown is not routine, and both now pass the default
  notification filter. They appear amber in the event log from now on.
• Webhook posts check the HTTP status: a 404/401 from the target is written to the
  process log instead of passing silently. Notification failures still never affect the
  shutdown logic.
• Documentation touch-ups: the Proxmox user and API token in a cluster, NUT on a
  QNAP/Synology NAS, and community-scripts.org as an additional listing.