Add the SyncWorker and its cron configuration for Oban.

config/config.exs

@@ -8,7 +8,16 @@
 import Config
 
 config :ash_oban, pro?: false
-config :decentralised_book_index, Oban, plugins: [{Oban.Plugins.Cron, []}]
+config :decentralised_book_index, Oban,
+  repo: DecentralisedBookIndex.Repo,
+  queues: [default: 14],
+  plugins: [
+    Oban.Plugins.Pruner,
+    {Oban.Plugins.Cron,
+     crontab: [
+      {"@daily", DecentralisedBookIndex.SyncWorker},
+    ]}
+  ]
 
 config :mime,
   extensions: %{"json" => "application/vnd.api+json"},

lib/decentralised_book_index/sync/sync_workers/sync_worker.ex

@@ -0,0 +1,13 @@
+defmodule DecentralisedBookIndex.SyncWorker do
+  use Oban.Worker,
+    queue: :default,
+    max_attempts: 2,
+    tags: ["sync", "cron"]
+
+  require Logger
+
+  @impl Oban.Worker
+  def perform(%Oban.Job{args: args} = job) do
+    SyncServerTask.sync_all()
+  end
+end