Allow other controllers to access lndhub user balance

app/services/lndhub_manager/fetch_user_balance.rb

@@ -0,0 +1,12 @@
+module LndhubManager
+  class FetchUserBalance < Lndhub
+    def initialize(auth_token:)
+      @auth_token = auth_token
+    end
+
+    def call
+      data = fetch_balance(auth_token)
+      data["BTC"]["AvailableBalance"] rescue nil
+    end
+  end
+end