feat(typescript): add discriminated union auth configuration via anyAuth enum

[devin-ai-integration]

Description

Link to Devin run: https://app.devin.ai/sessions/04420b83e4c94f05bf2969c09e2c1722
Requested by: Niels Swimberghe (@Swimburger)

Adds a new anyAuth config option to the TypeScript SDK generator. When set to v2, users explicitly choose the auth type via a discriminated union with a type field, instead of the default v1 behavior where the SDK tries each auth method and catches errors.

Changes Made

• Added anyAuth: "v1" | "v2" config option to TypescriptCustomConfigSchema
• Created AnyAuthV2ProviderGenerator and AnyAuthV2ProviderInstance classes
• Updated BaseClientTypeGenerator to generate AnyAuthProvider.AuthOptions when anyAuth: v2
• Updated AuthProvidersGenerator to support the new "anyAuthV2" auth scheme type
• Added seed test fixture any-auth/discriminated-union-auth with anyAuth: v2 config
• Added changelog entry for v3.38.0

Example usage with anyAuth: v2:

# In generators.yml
config:
  anyAuth: v2

const client = new Client({
  auth: {
    type: "Bearer",
    token: "YOUR_BEARER_TOKEN"
  }
});

const client = new Client({
  auth: {
    type: "OAuth",
    clientId: "...",
    clientSecret: "..."
  }
});

Updates since last revision

Addressed PR feedback to pass normalized options to all auth providers:

• Changed constructor type from BaseClientOptions & AnyAuthProvider.AuthOptions to just BaseClientOptions (since BaseClientOptions already includes AuthOptions via intersection)
• Use options.auth directly in switch statement - TypeScript narrows the type within each case
• Pass { ...options, ...options.auth } to ALL auth providers (Bearer, Header, Basic, OAuth) - this flattens the auth fields to the top level, matching how providers are constructed in non-any-auth fixtures
• Removed any cast in default case error message

Testing

• Seed tests pass for any-auth fixture (all 3 configurations)
• Lint checks pass
• Unit tests added/updated

Human Review Checklist

• Options spreading: Verify { ...options, ...options.auth } correctly flattens auth fields to top level for each provider type
• Type compatibility: The spread object should satisfy each provider's Options type (which extends AuthOptions)
• Undefined auth fallback: When auth is undefined, the constructor creates a NoOpAuthProvider delegate. Verify this is the desired behavior vs. throwing an error.
• Discriminator values: The type field values (e.g., "Bearer", "ApiKey", "OAuth") are derived from the auth scheme key in the IR. Verify these match expected user-facing values.

[devin-ai-integration]

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[fern-support]

No, it should be new BearerAuthProvider(options);.
update the generators so they accept the normalized options, joined with the bearer specific auth.
Do the same for other schemes