Revert "Migrates alerts to an object-oriented implementation"

This reverts commit fbc283f12f.

scripts/lua/modules/alert_definitions/alert_udp_unidirectional.lua

@@ -2,42 +2,22 @@
 -- (C) 2019-20 - ntop.org
 --
 
--- ##############################################
-
 local alert_keys = require "alert_keys"
-package.path = dirs.installdir .. "/scripts/lua/modules/?.lua;" .. package.path
 
-local status_keys = require "flow_keys"
--- Import the classes library.
-local classes = require "classes"
--- Make sure to import the Superclass!
-local alert = require "alert"
+-- @brief Prepare an alert table used to generate the alert
+-- @param alert_severity A severity as defined in `alert_severities`
+-- @return A table with the alert built
+local function createUDPUnidirectional()
+   local built = {
+      alert_type_params = {},
+   }
 
--- ##############################################
+   return built
+end
 
-local alert_udp_unidirectional = classes.class(alert)
-
--- ##############################################
-
-alert_udp_unidirectional.meta = {
-  status_key = status_keys.ntopng.status_udp_unidirectional,
+return {
   alert_key = alert_keys.ntopng.alert_udp_unidirectional,
   i18n_title = "flow_details.udp_unidirectional",
   icon = "fas fa-info-circle",
+  creator = createUDPUnidirectional,
 }
-
--- ##############################################
-
--- @brief Prepare an alert table used to generate the alert
--- @return A table with the alert built
-function alert_udp_unidirectional:init()
-   -- Call the parent constructor
-   self.super:init()
-
-   self.alert_type_params = {}
-end
-
--- #######################################################
-
-return alert_udp_unidirectional
-