Domain Names host check (#5723)

* Adding/modifying .cpp for Domain Names host check

* Adding/modifying .h/.lua for Domain Names host check

* minor synstax fix

* dns_contacts

Co-authored-by: Stefano Russo <55586218+D0kken@users.noreply.github.com>
Co-authored-by: Stefano Russo <s.russo41@studenti.unipi.it>

scripts/lua/modules/alert_definitions/host/host_alert_domain_names_contacts.lua

@@ -0,0 +1,63 @@
+--(C) 2019-21 - ntop.org
+
+
+--##############################################
+
+local host_alert_keys = require "host_alert_keys"
+package.path = dirs.installdir .. "/scripts/lua/modules/?.lua;" .. package.path
+local alert_creators = require "alert_creators"
+local json = require("dkjson")
+--Import the classes library.
+local classes = require "classes"
+--Make sure to import the Superclass!
+local alert = require "alert"
+
+--##############################################
+
+local host_alert_domain_names_contacts = classes.class(alert)
+
+--##############################################
+
+host_alert_domain_names_contacts.meta = {
+alert_key = host_alert_keys.host_alert_domain_names_contacts,
+i18n_title =  "alerts_dashboard.threashold_cross",
+icon = "fas fa-fw fa-arrow-circle-up",
+
+}
+
+--##############################################
+
+--@brief Prepare an alert table used to generate the alert
+--@param one_param The first alert param
+--@param another_param The second alert param
+--@return A table with the alert built
+function host_alert_domain_names_contacts:init()
+--Call the parent constructor
+self.super:init()
+
+end
+
+--#######################################################
+
+-- @brief Format an alert into a human-readable string
+-- @param ifid The integer interface id of the generated alert
+-- @param alert The alert description table, including alert data such as the generating entity, timestamp, granularity, type
+-- @param alert_type_params Table `alert_type_params` as built in the `:init` method
+-- @return A human-readable string
+function host_alert_domain_names_contacts.format(ifid, alert, alert_type_params)
+  local alert_consts = require("alert_consts")
+  local entity = alert_consts.formatHostAlert(ifid, alert["ip"], alert["vlan_id"])
+  local value = alert_type_params.value
+
+  if(value == nil) then value = 0 end
+
+  return i18n("alert_messages.host_alert_domain_names_contacts", {
+    entity = entity,
+    value = string.format("%u", math.ceil(value or 0)),
+    threshold = alert_type_params.threshold or 0,
+  })
+end
+
+--#######################################################
+
+return host_alert_domain_names_contacts