Adds hasToken method

LeStorage/Services.swift

@@ -357,6 +357,15 @@ public class Services {
         try self.keychainStore.deleteToken()
     }
     
+    public func hasToken() -> Bool {
+        do {
+            _ = try self.keychainStore.getToken()
+            return true
+        } catch {
+            return false
+        }
+    }
+    
     /// Parse a json data and tries to extract its error message
     /// - Parameters:
     ///  - data: some JSON data