GP Values and Double OptIn

[cyrotek]

Hey, first and foremost thanks for the plugin and your effort to maintain it!

So, I've a form where I use a predefined set of recievers, based upon a select within the form. Just like in the example here: https://github.com/in2code-de/powermail/blob/develop/Documentation/ForAdministrators/BestPractice/DynamicReceiver.md#dynamic-example-1

Though, it doesn't seem to work, I did find that bug where you stated that there are no GP values available within the Optin process, though, how would one setup dynamic receivers then? Here is the bug mentioned: https://github.com/in2code-de/powermail/issues/455

Best wishes, Sebastian