Add actor field to subscription contract and billing attempt mutations

We have introduced a new actor field in subscription mutations to help you track who initiated an action - whether it was the customer, the merchant, or the partner app's automated system.

You can now include an actor argument when creating billing attempts or editing subscription contracts. This field accepts the following values:

• customer: The buyer initiated the action (e.g., clicking "pay now" in a customer portal).
• merchant: A merchant or their staff manually initiated the action.
• partner: The partner app's automated system initiated the action (e.g., scheduled billing or retry logic).

This field is available in the following Admin API mutations:

Billing Attempts:

• subscriptionBillingAttemptCreate (via subscriptionBillingAttemptInput.actor)
• subscriptionBillingCycleCharge
• subscriptionBillingCycleBulkCharge

Contract Edits:

• subscriptionContractCreate
• subscriptionContractUpdate
• subscriptionContractAtomicCreate
• subscriptionContractProductChange
• subscriptionBillingCycleContractEdit

Status Updates:

• subscriptionContractActivate
• subscriptionContractPause
• subscriptionContractCancel
• subscriptionContractFail
• subscriptionContractExpire