curl --request POST \
  --url https://api.ubicloud.com/project/{project_id}/location/{location}/postgres/{postgres_database_reference}/set-maintenance-window \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '{
  "maintenance_window_start_at": 123
}'

{
  "flavor": "<string>",
  "ha_type": "<string>",
  "id": "pgn30gjk1d1e2jj34v9x0dq4rp",
  "location": "<string>",
  "name": "<string>",
  "state": "<string>",
  "storage_size_gib": 123,
  "target_storage_size_gib": 123,
  "version": "<string>",
  "vm_size": "<string>",
  "target_vm_size": "<string>",
  "ca_certificates": "<string>",
  "maintenance_window_start_at": 123,
  "read_replica": true,
  "parent": "<string>",
  "tags": [
    {
      "key": "<string>",
      "value": "<string>"
    }
  ],
  "connection_string": "<string>",
  "earliest_restore_time": "<string>",
  "firewall_rules": [
    {
      "cidr": "<string>",
      "description": "<string>",
      "id": "pfmjgkgbktw62k53005jpx8tt7"
    }
  ],
  "latest_restore_time": "<string>",
  "primary": true
}