Quality of life improvements I

We added a couple of improvements to several parts of our API especially on your possibilities to maintain callback subscriptions.

Callback management

We improved the management of subscriptions/callbacks

• Consumers are now able to edit existing subscriptions simply by calling the respective POST endpoints with the updated payload.
• We are introducing a new endpoint to fetch your current callback configuration: GET api/subscriptions. It returns a list of all active subscriptions.
• Once the cardUpdated callback is sent for card updates (e.g. because the event CARD_DETAILS_CHANGED has happened) and no changes are made to the card limits the limitChangeproperty will be omitted from the payload from now on.

Minor improvements

• Previously it was possible to issue a card for a member in INACTIVE state. This is not possible anymore. Instead, the API will respond with HTTP status codes 404 and errorCode NOT_FOUND.
• We added cardholderId to transactionUpdated object that is sent for callbacks that can be subscribed via POST /transactions/subscription.