Add Subscription for app

The secondary subscription callback URL. The events delivered on the primary callback URL is also forwarded to this secondary subscription.

The tag of a callback URL can be used to identify the subscription

Modes is used to enable specific events for the subscription URL. Possible values: NONE(0, 0), SENT(1, 0), DELIVERED(2, 1), READ(4, 2), DELETED(8, 3), OTHERS(16, 4), COPY(32, 5), MESSAGE(64, 6), TEMPLATE(128,7), ACCOUNT(256,8), BILLING(512,8). The numeric value addition can also be used. For example, adding SENT and READ events to a subscription is done using values (1, 0) + (4, 2) = (5, 3). OR you can pass the values SENT, READ.

This flag will check if the subscription URL already exists.

unique identifier for an account