Host Pools UI changes

- Do now show the "Not Assigned" group in user pool dropdown
- Show an alert message when creating a Captive Portal user and no pools are defined
- Improve unique member validator to account missing network prefixes
- Prevent deleting an Host Group when a captive portal user is defined on it

scripts/lua/modules/host_pools_utils.lua

@@ -7,7 +7,7 @@ package.path = dirs.installdir .. "/scripts/lua/modules/?/init.lua;" .. package.
 
 local host_pools_utils = {}
 host_pools_utils.DEFAULT_POOL_ID = "0"
-host_pools_utils.DEFAULT_POOL_NAME = "Default"
+host_pools_utils.DEFAULT_POOL_NAME = "Not Assigned"
 host_pools_utils.MAX_NUM_POOLS = 16
 host_pools_utils.MAX_MEMBERS_NUM = 32
 
@@ -23,6 +23,10 @@ local function get_pool_details_key(ifid, pool_id)
   return "ntopng.prefs." .. ifid .. ".host_pools.details." .. pool_id
 end
 
+local function get_user_pool_id_key(username)
+  return "ntopng.user." .. username .. ".host_pool_id"
+end
+
 local function get_pool_detail(ifid, pool_id, detail)
   local details_key = get_pool_details_key(ifid, pool_id)
 
@@ -106,4 +110,19 @@ function host_pools_utils.initPools()
   end
 end
 
+function host_pools_utils.getUndeletablePools()
+  -- TODO fix interface-local pools VS global users inconsistence
+  local key = get_user_pool_id_key("*")
+  local pools = {}
+
+  for user_key,_ in pairs(ntop.getKeysCache(key) or {}) do
+    local pool_id = ntop.getCache(user_key)
+    if tonumber(pool_id) ~= nil then
+        pools[pool_id] = true
+    end
+  end
+
+  return pools
+end
+
 return host_pools_utils