Implement Zod: discriminatedUnion

[Georgegriff]

Hello, I notice currently the openapi discriminator with mapping when used with "oneOf" does not generatezod.discriminatedUnioncode, they instead chainor's` which can result in slightly wrong error messages from zod. Is there a reason this was avoided or could it make sense?

I'm happy to investigate implementing, just thought I'd ask first, i'm not sure if doing so would be a breaking change or a correction.

[melloware]

Feel free to investigate and provide a PR!

[Georgegriff]

started working on it, running the code locally comes with some challenges:

Error [ERR_REQUIRE_ESM]: require() of ES Module /.../node_modules/ansi-styles/index.js from /.../orval/packages/core/node_modules/chalk/source/index.js not supported.

Was trying to run one of the samples to get a feel for how the code works

EDIT: fixed, had to recursively delete my node_modules folder and then re-run yarn install. PAIN!