sent-integration-starterlisted

# Sent Integration Starter Bring up a Sent integration in four stages: authenticate, send idempotently, receive verified events, then harden. Do not conflate them — most broken integrations pass stage one and skip stage three. ## Stage 1: client and credentials Direct Sent v3 REST requests authenticate with the `x-api-key` header. An application proxy may accept `Authorization: Bearer` from its own callers, and the Sent MCP server uses client-managed OAuth, but neither changes the REST header sent to `api.sent.dm`. Organization keys may add `x-profile-id` to act for a child profile; a profile-scoped key that sends that header receives `403`. | Language | Package | Client | | --- | --- | --- | | TypeScript | `@sentdm/sentdm` | `new SentDm()` | | Python | `sentdm` (imports `sent_dm`) | `Sent()` or `AsyncSent()` | | Go | `github.com/sentdm/sent-dm-go` | `sentdm.NewClient()` | | Java | `dm.sent:sent-java` | `SentOkHttpClient.fromEnv()` | | C# | `Sentdm` | `new SentClient()` | | PHP | `sentdm/sent-dm-php` | `new SentDm\Client($apiKey)` | | Ruby | `sentdm` | `Sentdm::Client.new` | Every SDK except PHP reads `SENT_DM_API_KEY` automatically. Single-endpoint receiver samples read `SENT_DM_WEBHOOK_SECRET`; multi-tenant production receivers need a secret registry keyed by webhook id instead of one process-wide secret. Older documentation uses `SENT_API_KEY` and `SENT_WEBHOOK_SECRET` — treat those as aliases and standardize on the `SENT_DM_` names. Choose the client lifecycle from