sinch-authenticationlisted

# Sinch Authentication Cross-cutting skill that covers credential setup and authentication for all Sinch APIs. Determines the correct auth model, provides curl examples, SDK init code, and troubleshooting for common auth errors. ## Agent Instructions If the user hasn't specified which Sinch product they're integrating, ask first — the auth model depends on the product. Use the decision table in Step 1 to route to the correct credentials. ## Step 1: Identify the Auth Model Determine which model applies based on the Sinch product: | Auth Model | Products | Credentials Needed | |-----------|----------|-------------------| | **Project-scoped** (Basic or OAuth2) | Conversation API, Numbers, Fax, EST, 10DLC, Number Lookup, Provisioning | Project ID + Key ID + Key Secret | | **Application-scoped** (Basic or Signed) | Voice API, Verification API, In-App Calling SDKs | Application Key + Application Secret | | **API key** | Mailgun | API Key (username is literal `api`) | > Voice/Verification credentials are a **separate credential set** from project Access Keys (different dashboard pages and auth models). In multi-product SDK clients, you may provide both sets together, but do not substitute one set for the other. ## Step 2: Get Credentials - **Project-scoped**: Dashboard > Settings > Access Keys → creates Key ID + Key Secret. Project ID is at the top of the dashboard. - **Application-scoped**: Dashboard > Voice > Apps or Verification > Apps → creates Application Key + Applica