Function isFederatedDomain

isFederatedDomain(
    auth0Domain: string,
    emailDomain: string,
    options?: IsFederatedDomainOptions,
): Promise<boolean>
Checks whether an email domain is managed for enterprise SSO on an Auth0 tenant.

This is a routing hint, not a security control. Always validate the org_id claim on the resulting ID token regardless of what this returns.

Server-side only. Calling this from the browser would expose the Auth0 domain and allow clients to enumerate your customers' domains.
Parameters
- auth0Domain: string
  Your Auth0 tenant domain, e.g. your-tenant.auth0.com.
- emailDomain: string
  The domain part of the user's email, e.g. acmecorp.com. Case-insensitive.
- Optionaloptions: IsFederatedDomainOptions
  Optional customFetch and timeoutMs overrides.
Returns Promise<boolean>
true only when Auth0 has an enterprise connection or organization domain-discovery record for the domain. Returns false on any error, so a WebFinger outage degrades to your existing login flow rather than blocking it.
Example
```
const emailDomain = email.split("@")[1];
if (await isFederatedDomain(process.env.AUTH0_DOMAIN!, emailDomain)) {
  // route through Auth0 SSO
} else {
  // route through your existing login
}
```
- Defined in src/utils/webfingerCache.ts:78