Remove Subscription from Group

Adds an existing subscription to a subscription group. For sites making use of the [Relationship Billing](https://maxio.zendesk.com/hc/en-us/articles/24252287829645-Advanced-Billing-Invoices-Overview) and [Customer Hierarchy](https://maxio.zendesk.com/hc/en-us/articles/24252185211533-Customer-Hierarchies-WhoPays#customer-hierarchies) features, it is possible to add existing subscriptions to subscription groups. Passing `group` parameters with a `target` containing a `type` and optional `id` is all that's needed. When the `target` parameter specifies a `"customer"` or `"subscription"` that is already part of a hierarchy, the subscription will become a member of the customer's subscription group. If the target customer or subscription is not part of a subscription group, a new group will be created and the subscription will become part of the group with the specified target customer set as the responsible payer for the group's subscriptions. **Note:** In order to add an existing subscription to a subscription group, it must belong to either the same customer record as the target, or be within the same customer hierarchy. Rather than specifying a customer, the `target` parameter could instead simply have a value of * `"self"` which indicates the subscription will be paid for not by some other customer, but by the subscribing customer, * `"parent"` which indicates the subscription will be paid for by the subscribing customer's parent within a customer hierarchy, or * `"eldest"` which indicates the subscription will be paid for by the root-level customer in the subscribing customer's hierarchy. To create a new subscription into a subscription group, reference the following: [Create Subscription in a Subscription Group](https://developers.chargify.com/docs/api-docs/d571659cf0f24-create-subscription#subscription-in-a-subscription-group)