[hiradp]

Add commands to view and set a Postgres branch's maintenance window, and to list, show and reschedule its scheduled maintenance.

pscale branch maintenance window show <database> <branch>
pscale branch maintenance window set <database> <branch> [--day <day>] [--hour <0-23>]
pscale branch maintenance event list <database> <branch> [--state <state>]
pscale branch maintenance event show <database> <branch> <event>
pscale branch maintenance event reschedule <database> <branch> <event> --to <time>

• The window's day and hour are in UTC. window show also prints the next window in local time, and window set sends nothing when the window wouldn't change.
• reschedule --to must be one of the event's available times. The command checks it before sending and lists the valid times when it isn't one.
• The client gains MaintenanceSchedules.Update and a MaintenanceEvents service. Schedules now include their branch, which pscale maintenance list and show print in a new column.
• The branch maintenance help no longer says images are upgraded only in emergencies.

Security Impact: None