Add credential scope update

[herber]

Note

Medium Risk
Extends the SDK update request shape for provider auth credentials to include clientId, clientSecret, and scopes, which touches credential/secret handling (even though it’s just client-side mapping). Risk is limited to request serialization compatibility with the API.

Overview
Adds support for updating OAuth credential fields via the generated SDK. The *AuthCredentialsUpdateBody types and mappers now accept client_id, client_secret, and scopes (string array) in addition to name, description, and metadata.

This change is applied consistently across both API versions (mt_2025_01_01_dashboard and mt_2026_01_01_magnetar) and across dashboard/management and non-instance provider-deployment auth-credential update resources.

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