GET /v1/subscription/{handle}/upgrade

{
  "current_plan": {
    "name": "Fitness",
    "description": "Fitness 149/month subscription",
    "vat": 0.25,
    "amount": 25000,
    "quantity": 3,
    "prepaid": true,
    "handle": "plan02",
    "version": 1,
    "state": "active",
    "currency": "DKK",
    "dunning_plan": "dunning_plan_02",
    "tax_policy": "default_tax_policy_handle",
    "renewal_reminder_email_days": 7,
    "trial_reminder_email_days": 7,
    "partial_period_handling": "bill_prorated",
    "include_zero_amount": true,
    "setup_fee": 10000,
    "setup_fee_text": "Subscription setup fee",
    "setup_fee_handling": "first",
    "setup_fee_vat": 0.2,
    "setup_fee_tax_policy": "setup_fee_tax_policy_handle",
    "setup_fee_amount_incl_vat": true,
    "partial_proration_days": true,
    "fixed_trial_days": true,
    "minimum_prorated_amount": 100,
    "account_funding": true,
    "cost_object": "KT-4711",
    "amount_incl_vat": true,
    "fixed_count": 12,
    "fixed_life_time_unit": "months",
    "fixed_life_time_length": 12,
    "trial_interval_unit": "months",
    "trial_interval_length": 1,
    "interval_length": 12,
    "schedule_type": "month_startdate",
    "schedule_fixed_day": 12,
    "base_month": 1,
    "notice_periods": 1,
    "fixation_periods": 3,
    "fixation_period_unit_type": "month",
    "notice_period_unit_type": "month",
    "contract_period": 12,
    "contract_period_unit_type": "month",
    "contract_period_after_renewal_period": 6,
    "contract_period_after_renewal_unit_type": "month",
    "subscription_duration_type": "auto_renew",
    "effective_setup_fee_vat": 0.25,
    "effective_setup_fee_amount_incl_vat": true
  },
  "configuration_handle": "config_001",
  "available_upgrade_paths": [
    {
      "target_plan": {
        "name": "Fitness",
        "description": "Fitness 149/month subscription",
        "vat": 0.25,
        "amount": 25000,
        "quantity": 3,
        "prepaid": true,
        "handle": "plan02",
        "version": 1,
        "state": "active",
        "currency": "DKK",
        "dunning_plan": "dunning_plan_02",
        "tax_policy": "default_tax_policy_handle",
        "renewal_reminder_email_days": 7,
        "trial_reminder_email_days": 7,
        "partial_period_handling": "bill_prorated",
        "include_zero_amount": true,
        "setup_fee": 10000,
        "setup_fee_text": "Subscription setup fee",
        "setup_fee_handling": "first",
        "setup_fee_vat": 0.2,
        "setup_fee_tax_policy": "setup_fee_tax_policy_handle",
        "setup_fee_amount_incl_vat": true,
        "partial_proration_days": true,
        "fixed_trial_days": true,
        "minimum_prorated_amount": 100,
        "account_funding": true,
        "cost_object": "KT-4711",
        "amount_incl_vat": true,
        "fixed_count": 12,
        "fixed_life_time_unit": "months",
        "fixed_life_time_length": 12,
        "trial_interval_unit": "months",
        "trial_interval_length": 1,
        "interval_length": 12,
        "schedule_type": "month_startdate",
        "schedule_fixed_day": 12,
        "base_month": 1,
        "notice_periods": 1,
        "fixation_periods": 3,
        "fixation_period_unit_type": "month",
        "notice_period_unit_type": "month",
        "contract_period": 12,
        "contract_period_unit_type": "month",
        "contract_period_after_renewal_period": 6,
        "contract_period_after_renewal_unit_type": "month",
        "subscription_duration_type": "auto_renew",
        "effective_setup_fee_vat": 0.25,
        "effective_setup_fee_amount_incl_vat": true
      },
      "self_upgrade_allowed": true
    }
  ]
}