Create a new plan

{
    "plan": {
        "name": "Monthly Plan",
        "description": "Monthly Plan",
        "selling_plans": [
            {
                "delivery_policy": {
                    "frequency": 1,
                    "interval": "month",
                    "auto_expire": {
                        "frequency": 12,
                        "interval": "month"
                    },
                    "anchors": {
                        "type": "MONTHDAY",
                        "value": [10, 20]
                    },
                    "pre_anchor_behavior": "ASAP",
                    "cutoff": 0
                },
                "billing_policy": {
                    "frequency": 1,
                    "interval": "month"
                },
                "pricing_polices": [
                    {
                        "discount": {
                            "type": "percentage",
                            "value": 50
                        }
                    }
                ]
            }
        ]
    }
}