Release v3.0.0

Breaking changes

Handler success arms are now sealed — direct Ok((StatusCode, Json(...))) construction no longer compiles when the rfc-types feature is active (the new default).

Before:

async fn get_item(id: Uuid) -> HandlerResponse<Item> {
    let item = fetch(id).await?;
    Ok((StatusCode::OK, Json(ApiResponse::builder(item).build())))  // ← no longer compiles
}

After: Use the existing builder functions, which already produce the correct type:

async fn get_item(id: Uuid) -> HandlerResponse<Item> {
    let item = fetch(id).await?;
    ok(item)  // ← unchanged call site; now the only valid path
}

The Ok arm of each type alias has changed:

Type alias	Before	After
HandlerResponse<T>	(StatusCode, Json<ApiResponse<T>>)	RfcOk<T>
CreatedResponse<T>	(StatusCode, Json<ApiResponse<T>>)	RfcOk<T>
CreatedAtResponse<T>	(StatusCode, HeaderMap, Json<ApiResponse<T>>)	RfcOk<T>
EtaggedHandlerResponse<T>	(StatusCode, ETag, Json<ApiResponse<T>>)	RfcOk<T>
HandlerListResponse<T>	Json<ApiResponse<PaginatedResponse<T>>>	RfcOk<PaginatedResponse<T>>

created_under now requires T: Serialize (previously deferred to axum).

Added

• RfcOk<T> — sealed success wrapper produced by all builder functions.
  Exposes .status(), .headers(), and .body_json() for inspection.
  Cannot be constructed outside this crate. Gated on rfc-types.

• UnconstrainedResponse — explicit, always-available opt-out for routes
  whose wire format is externally mandated. Each use must be documented at the
  call site with a product-level justification. See ADR platform/0020.

• rfc-types feature (default: enabled) — enables the sealed RfcOk<T>
  types. Disable only during a migration window; prefer UnconstrainedResponse
  for per-handler opt-outs.

Migration

1. Replace Ok((StatusCode::..., Json(...))) in handler bodies with the
   builder functions (ok, created, etc.). Handlers already using the
   builders need no changes.

2. Update tests that destructured the Ok arm:

   // before
   let (status, body) = ok(x).unwrap();
   // after
   let resp = ok(x).unwrap();
   assert_eq!(resp.status(), StatusCode::OK);
   assert_eq!(resp.body_json()["data"], expected);

3. Routes that bypass the envelope (e.g. OpenAI-compatible endpoints) must
   return UnconstrainedResponse with an explanatory comment.

4. To restore old behaviour during a migration window:

   socle = { version = "3", default-features = false, features = ["telemetry", "database", ...] }