Reworks plugin loading and structure

Implements #4358

scripts/plugins/alerts/internals/alerts_drops/user_scripts/system/dropped_alerts.lua

@@ -0,0 +1,58 @@
+--
+-- (C) 2019-20 - ntop.org
+--
+
+local user_scripts = require("user_scripts")
+local alerts_api = require("alerts_api")
+local alert_consts = require("alert_consts")
+
+local script = {
+  -- Script category
+  category = user_scripts.script_categories.internals,
+
+  -- This script is only for alerts generation
+  is_alert = true,
+
+  -- See below
+  hooks = {},
+
+  gui = {
+    i18n_title = "internals.alert_drops",
+    i18n_description = "internals.alert_drops_descr",
+  },
+}
+
+-- #################################################################
+
+function script.hooks.min(params)
+  local available_interfaces = interface.getIfNames()
+
+  -- Add the system interface id
+  available_interfaces[getSystemInterfaceId()] = getSystemInterfaceName()
+
+  for _, iface in pairs(available_interfaces) do
+    interface.select(iface)
+
+    local new_dropped_alerts = interface.checkDroppedAlerts()
+
+    local alert_type = alert_consts.alert_types.alert_dropped_alerts.create(
+       alert_consts.alert_severities.error,
+       alert_consts.alerts_granularities.min,
+       interface.getId(),
+       new_dropped_alerts
+    )
+
+    -- Note: required for the trigger/release below
+    interface.select(getSystemInterfaceId())
+
+    if(new_dropped_alerts > 0) then
+      alerts_api.trigger(params.alert_entity, alert_type, nil, params.cur_alerts)
+    else
+      alerts_api.release(params.alert_entity, alert_type, nil, params.cur_alerts)
+    end
+  end
+end
+
+-- #################################################################
+
+return script