A budget is a plan that describes what you expect to spend
on Cloud projects, plus the rules to execute as spend is tracked against
that plan, (for example, send an alert when 90% of the target spend is
met). Currently all plans are monthly budgets so the usage period(s)
tracked are implied (calendar months of usage back-to-back).
User data for display name in UI. Validation: <= 60 chars.
Required. Budgeted amount.
Optional. Rules to apply to all updates to the actual spend,
regardless of the thresholds set in threshold_rules.