New max_units field on app subscription queries

You can now query the max_units field on app_subscription queries.

• For seat-based apps, this will return the maximum number of seats allowed.
• For feature-based apps, this will return null.

query {
  app_subscription {
    billing_period
    days_left
    is_trial
    plan_id
    renewal_date
    max_units
  }
}