Get invoice

{  "id": "inv_1a2b3c4d",  "customerId": "cus_1a2b3c4d",  "subscriptionId": "sub_1a2b3c4d",  "invoiceNumber": "INV-2026-0001",  "status": "paid",  "invoiceType": "recurring",  "currency": "usd",  "subtotal": 2000,  "discountAmount": 0,  "taxAmount": 0,  "total": 2000,  "periodStart": "2026-09-07T12:00:00.000Z",  "periodEnd": "2026-10-07T12:00:00.000Z",  "issueDate": "2026-09-07T12:00:00.000Z",  "dueDate": "2026-09-07T12:00:00.000Z",  "memo": null,  "metadata": {},  "createdAt": "2026-09-07T12:00:00.000Z",  "updatedAt": "2026-09-07T12:00:00.000Z",  "creditApplied": 0,  "planName": "Pro",  "poNumber": null,  "reference": null,  "lineItems": [    {      "lineType": "plan_base",      "featureName": null,      "description": "Pro — monthly subscription",      "quantity": 1,      "unitAmount": 2000,      "amount": 2000,      "includedAmount": null,      "usedAmount": null,      "overageAmount": null,      "discountType": null,      "discountValue": null,      "discountName": null,      "chargeType": "standard"    }  ],  "object": "invoice",  "livemode": false}

{  "error": {    "type": "validation_error",    "code": "validation_error",    "message": "The request contains an invalid parameter.",    "doc_url": "https://commet.co/docs/api-reference/2026-08-27/errors/validation_error.md"  }}

{  "error": {    "type": "authentication_error",    "code": "unauthorized",    "message": "A valid API key is required.",    "doc_url": "https://commet.co/docs/api-reference/2026-08-27/errors/unauthorized.md"  }}

{  "error": {    "type": "authentication_error",    "code": "forbidden",    "message": "You do not have permission to perform this operation.",    "doc_url": "https://commet.co/docs/api-reference/2026-08-27/errors/forbidden.md"  }}

{  "error": {    "type": "not_found_error",    "code": "not_found",    "message": "The requested resource was not found.",    "doc_url": "https://commet.co/docs/api-reference/2026-08-27/errors/not_found.md"  }}

{  "error": {    "type": "rate_limit_error",    "code": "rate_limited",    "message": "Too many requests. Retry after the interval specified in the Retry-After header.",    "doc_url": "https://commet.co/docs/api-reference/2026-08-27/errors/rate_limited.md"  }}

{  "error": {    "type": "internal_error",    "code": "internal_error",    "message": "An unexpected error occurred while processing the request.",    "doc_url": "https://commet.co/docs/api-reference/2026-08-27/errors/internal_error.md"  }}