Add rate-limiting on queries with Hammer

Closes #67

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

config/config.exs

@@ -321,6 +321,9 @@ config :mobilizon, Oban,
     {Oban.Plugins.Pruner, max_age: 300}
   ]
 
+config :hammer,
+  backend: {Hammer.Backend.ETS, [expiry_ms: 60_000 * 60 * 4, cleanup_interval_ms: 60_000 * 10]}
+
 config :mobilizon, :rich_media,
   parsers: [
     Mobilizon.Service.RichMedia.Parsers.OEmbed,