Shared secret for the Remote config

[kendy]

To be able to add access token for the convert-to endpoint, it is necessary to setup trusted communication between the COOL and integration for Remote config.

The idea is that the Remote config URL will contain a token, that will be then used while requesting the Remote config from the integration.

Then - this remote config will define a token for the the convert-to endpoint.

@juliushaertl: Please do you have a preferred format for those URL's / tokens?