feature: IP filtering on signup page

disable registration form on IP not in range
checking the CIDR list before filtering with it
placing the cidr filters as an attribute object in the config

shared/models/server/server-config.model.ts

@@ -15,7 +15,8 @@ export interface ServerConfig {
   }
 
   signup: {
-    allowed: boolean
+    allowed: boolean,
+    allowedForCurrentIP: boolean
   }
 
   transcoding: {