ResourceIdentifier: [required] The RDS Amazon Resource Name (ARN) of the resource that the pending maintenance action applies to. For information about creating an ARN, see Constructing an RDS Amazon Resource Name (ARN).
ApplyAction: [required] The pending maintenance action to apply to this resource.
OptInType: [required] A value that specifies the type of opt-in request, or undoes an opt-in request. An opt-in request of type immediate can't be undone.
Valid Values:
immediate - Apply the maintenance action immediately.
next-maintenance - Apply the maintenance action during the next maintenance window for the resource.
undo-opt-in - Cancel any existing next-maintenance opt-in requests.