Function validateAttributes

validateAttributes(
    platformUrl: string,
    authProvider: AuthProvider,
    fqns: string[],
): Promise<void>
Checks that all provided attribute value FQNs exist on the platform. Validates FQN format first, then verifies existence via the platform API.

Use this before createZTDF() to catch missing or misspelled attributes early instead of discovering the problem at decryption time.
Parameters
- platformUrl: string
  The platform base URL.
- authProvider: AuthProvider
  An auth provider for the request.
- fqns: string[]
  Attribute value FQNs to validate, in the form https://<namespace>/attr/<name>/value/<value>.
Returns Promise<void>
Throws
AttributeNotFoundError if any FQNs are not found on the platform.

Throws
ConfigurationError if the FQN format is invalid or there are too many FQNs.
Example
```
await validateAttributes(platformUrl, authProvider, [
  'https://opentdf.io/attr/department/value/marketing',
]);
// Safe to encrypt — all attributes confirmed present
```
- Defined in src/policy/discovery.ts:107