Shared repository subscription management
4 operations.
/v1/graphs/{graph_id}/subscriptionsDetects resource type automatically: user graphs (kg) return the graph's subscription; shared repositories return the user's personal subscription to that repo.
/v1/graphs/{graph_id}/subscriptionsFor shared repositories only (sec, industry, etc.).
/v1/graphs/{graph_id}/subscriptionsFor repositories: synchronous tier change.
/v1/graphs/{graph_id}/subscriptions/cancelCancel a shared repository subscription.