RFC: BigInt support

[rand0m-cloud]

Description
In the OpenAPI spec for qdrant, we have this definition for an ID:

{
  "ExtendedPointId": {
    "description": "Type, used for specifying point ID in user interface",
    "anyOf": [
      {
        "type": "integer",
        "format": "uint64",
        "minimum": 0
      },
      {
        "type": "string",
        "format": "uuid"
      }
    ]
  }
}

This is causing issues in the JS REST client when the backend sends back a large number for an ID that is lost when converted to JS's number. I'm not sure how best to solve this issue because it feels like a breaking change. Currently, a number field is generated for number and integer fields in the OpenAPI spec.

Proposal
Generate a BigInt field when parsing a integer field in the OpenAPI spec.

[marcomuser]

I think you could use the transform option to generate BigInts for integers. See: https://github.com/drwpow/openapi-typescript/blob/main/docs/src/content/docs/v6/node.md#transform--posttransform

[drwpow]

As @marcomuser said, the transform() option is the preferred way to handle this. Remember that openapi-typescript has no runtime, and BigInt is not JSON-serializable. So how you instantiate that from your API is up to you (there is no singular, straightforward way to do this because you’re going to be overriding basic JSON deserialization), and openapi-typescript has no bearing on how that happens. So however you decide to solve that problem in your runtime code, just update openapi-typescript’s via transform() to match.

[drwpow]

Closed this issue because this is outside the scope of this library, however, I definitely think this should:

1. Be added to the docs examples (because others may have this problem)
2. Figure out a good solution for openapi-fetch to use this since it does have a runtime component