curl --request POST \
  --url https://us.api.flexprice.io/v1/taxes/associations \
  --header 'Content-Type: application/json' \
  --header 'x-api-key: <api-key>' \
  --data '
{
  "tax_rate_code": "<string>",
  "auto_apply": true,
  "currency": "<string>",
  "entity_id": "<string>",
  "entity_type": "customer",
  "external_customer_id": "<string>",
  "metadata": {},
  "priority": 123
}
'

{
  "auto_apply": true,
  "created_at": "<string>",
  "created_by": "<string>",
  "currency": "<string>",
  "entity_id": "<string>",
  "entity_type": "customer",
  "environment_id": "<string>",
  "id": "<string>",
  "metadata": {},
  "priority": 123,
  "status": "published",
  "tax_rate": {
    "code": "<string>",
    "created_at": "<string>",
    "created_by": "<string>",
    "description": "<string>",
    "environment_id": "<string>",
    "fixed_value": "<string>",
    "id": "<string>",
    "metadata": {},
    "name": "<string>",
    "percentage_value": "<string>",
    "scope": "INTERNAL",
    "status": "published",
    "tax_rate_status": "ACTIVE",
    "tax_rate_type": "percentage",
    "tenant_id": "<string>",
    "updated_at": "<string>",
    "updated_by": "<string>"
  },
  "tax_rate_id": "<string>",
  "tenant_id": "<string>",
  "updated_at": "<string>",
  "updated_by": "<string>"
}