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/check_definitions/host/domain_names_contacts.lua

@@ -0,0 +1,45 @@
+--
+-- (C) 2019-21 - ntop.org
+--
+
+local checks = require("checks")
+local host_alert_keys = require "host_alert_keys"
+
+local domain_names_contacts = {
+   -- Script category
+   category = checks.check_categories.network,
+
+   default_enabled = false,
+   alert_id = host_alert_keys.host_alert_domain_names_contacts,
+
+   -- The default threshold value. The format is specific of the
+   -- "threshold_cross" input builder
+   default_value = {
+      operator = "gt",
+      threshold = 250,
+   },
+
+   -- Allow user script configuration from the GUI
+   gui = {
+      -- Localization strings, from the "locales" directory of the plugin
+      i18n_title = "alerts_thresholds_config.domain_names_contacts_title",
+      i18n_description = "alerts_thresholds_config.domain_names_contacts_description",
+
+      -- Specific parameters of this input builder
+      i18n_field_unit = checks.field_units.contacts,
+
+      -- The input builder to use to draw the gui
+      input_builder = "threshold_cross",
+
+      -- max allowed threshold value
+      field_max = 65535,
+      -- min allowed threshold value
+      field_min = 1,
+      -- threshold check operator. "gt" for ">", "lt" for "<"
+      field_operator = "gt";
+   }
+}
+
+-- #################################################################
+
+return domain_names_contacts